Restricted mini challenges Cop's Thread

Question

Robber's thread

Your task as cops is to select three things:

• A programming language

• An OEIS sequence

• A byte set

You are then to secretly write a program in that language that computes the nth term sequence using only the bytes in the set. You will reveal the three pieces of information so that robbers can try to figure out the program.

Answers will be scored by the number of bytes in the byte set with more score being good. Cracked answers have an automatic score of 0. If your answer is uncracked after one week you may reveal the intended program and mark your answer as "safe".

Answers must be capable of calculating every term in the b-files of the sequence, but are not required to calculate any terms after.

Sequences can be either 1 or 0 indexed for both cops and robbers.

Here is a Python Script that checks if your code matches the given byte set.

Answer 1

Haskell, A209229, (cracked)

11 characters (including newline):

s<=[ ]
how!

Outputs True/False as an indicator function for powers of 2:

1 => True
2 => True
3 => False
4 => True
5 => False
6 => False
7 => False
8 => True
9 => False
...

Inputs are positive integers.

Answer 2

Python 2, A000045 (Cracked)

ml:= input(as,forge)

^{it contains a whitespace and a newline}
Try it Online!
Intended solution

Answer 3

Haskell, A000045 (cracked)

I made up my mind, I think I like t more than s.

So let's use these 30 bytes (including newline) instead:

abcdeFgh|jklmnopqrtTuvwxyz
=()

Please note that the general challenge description demands that

Answers must be capable of calculating every term in the b-files of the sequence [...].

In this case, the b-file goes up to the 2000th number, which is way beyond what can be computed using Int.

Answer 4

Octave, A000290, Cracked!

The sequence is the square numbers: 0, 1, 4, 9, 16, 25, 36, 49 ... (so that you don't have to check the link).

'()/@^_

Answer 5

Haskell, A000045 (Cracked)

Everyone likes Fibonacci numbers, I like Haskell...

I have carefully selected 30 bytes for you: the lowercase letters except f, i and t, you get the uppercase letters F and T and the pipe symbol | instead, and the three symbols =(), and newline. Here they are again:

abcdeFgh|jklmnopqrsTuvwxyz
=()

Answer 6

Haskell, A034262, 43 bytes, cracked

!"#%',.=?ABCDEFGHIJKLMNOPQRSTUVWXYZ[]_{|}~

Computes a(n) = n³ + n.

Answer 7

Haskell, A009056 (cracked)

Another simple one, now again with enough letters to make it look like ordinary Haskell and maybe for you to amaze me by finding a solution completely different from mine.

The sequence is Numbers >=3 and the charset consists of these 30 bytes:

{[abcdefghijklmnopqr uvwxyz]}.

---

The crack has some nice techniques. I was just thinking of this:

head . flip drop [ floor pi .. ]

Answer 8

C (C99), A000005, 25 Bytes#, Cracked!

These are the bytes for a full problem, takes n as a command line argument and outputs answer to stdout.(Space is included in bytecount).

<=>,;!"()*%+acdfhimnoprt 

Answer 9

Unary, A002275, 1 Byte

Byte set:

0

I had to at least try it :3

(I don't think it will be particularly hard seeing as every command in the language is available)

Answer 10

Perl 5, A000030 (Cracked)

Byte set:

imnprt7 $;()<>=~.

Try it online!

Answer 11

JavaScript (ES6), 17 bytes, A000290 (Cracked)

Again, this is the simple square sequence a(n) = n².

Byte set:

$()=>CI`abelotv{}

Answer 12

Hexagony, A057077, 77 bytes

Periodic sequence 1, 1, -1, -1. As a list:

a(0) = 1
a(1) = 1
a(2) = -1
a(3) = -1
a(4) = 1
a(5) = 1
a(6) = -1
   ...

Character set (edited), which includes a newline and a space character:

!%&(),0123456789;?@ABCDEFGHIJKLMOPQRSTUVWXYZ^abcdefghijklmnopqrstuvwxyz[]#. 

Try it online!

Answer 13

Haskell, A000045 (cracked)

It's cracked, and I won't start a new version, but if you want to play more: it's possible without y, and it's possible to be efficient.

---

I apologize for leading you in wrong directions by giving a g. Let's do the same without!

Here are the 29 remaining bytes (including newline):

abcdeFh|jklmnopqrtTuvwxyz
=()

Again, remember that Int won't be enough to compute the 2000th Fibonacci number which is needed because it is in the b-file.

Answer 14

Haskell, A000045 (cracked)

This is kindof (as announced) not a new version, but completely different. (Right?)

I still hope I can make you rediscover my nice little observation.

This time you are asked to implement the Fibonacci sequence using a charset of size 17, which (as far as I know) contains only one two unneeded chars:

eilnt=(,).[ ]_:0!

Note that there is no newline (but feel free to show a version which has them for readability) and remember that you have to be able to compute the 2000th Fibonacci number.

Answer 15

Cubix, A000027 (SAFE) 17 points

!&')-/0;@Oiru.NSQ

My solution:

!O!;i)!/u&!!r-)0'u;;!@

watch it online here

I originally did this without .NSQ but I figured I could add them safely.

Explanation:

This sequence is just "The Positive Integers". However, Cubix has three input commands, i, which reads in a single char (pushing -1 if input is empty), A, which reads in the rest of the input as chars (pushing a -1 to the bettom of the stack), and I, which reads the next number off the input (pushing 0 if there isn't a match). So naturally, I only provided i which reads in digits as their ascii value. uh-oh. Additionally, -1 is the usual marker for end of input, in conjunction with ? so I got rid of ?, forcing me to use ! (skip next instruction if TOS is not zero) for control flow. Finally, I thought I needed & to concatenate digits for printing with O (which outputs the top of stack as a number), but I realize now that that wasn't necessary either!

Another part of the challenge was originally to not have . the no-op character, but you can use pairs of ! instead if you're careful:

    ! O
    ! ;
i ) ! / u & ! !
r - ) 0 ' u ; ;
    ! @
    . .

i) : read input, increment.

!/ : if top of stack is zero (end of input), turn left

left: ;O.@ : pop top of stack, output as number, halt.

otherwise:

u'0: push char code of 0 to top of stack

)-r: increment, subtract, and rotate

;; : pop top of stack twice

u& : concatenate digits

!! : net zero effect, now we are at i) again.

Answer 16

Seed, A005408 (Odd Numbers) - Safe

Here's a slightly more challenging one. You may use any characters valid in Seed:

[0-9 ]

You shouldn't be able to brute force this one in a week unless you have a monster of a computer. Good luck! It's crackable.

Hint

This is the Befunge-98 program used in my solution: 9&2*1-.@ (the 9 can be removed, but my solution just happens to have one)

Solution

8 47142938850356537668025719950342285215695875470457212766920093958965599014291682211474803930206233718243166021324700185443274842742744297183042397910454208210130742260519105651032450664856693714718759816232968955289663444878636053035645231246428917992493766505872029989544065894418166685284738859999912471659057565000392419689361271972485444731284404987238803115210428572945108908191097214978382112218242627719651728712577306652405452922782307249485947045215982784790396555726144526602778473387279897334709142853151393812930171163300904436548870603006549005515709074682843356844201220668045057407146751793470423217099467145255174198241606814578351260769359571053755888106818197239116973006365593563235361647743411341624822052103816968153274122434280200888824954875622811325064255818154979564925710534165572852442761249176778416688044630942040966271963723430245979221181930857841829694362184653939393940015797332978459794253176110314873994228261888801228999293570329618551223457182420746927212801550646743152754821640064626761542582557138452651970009253770914346130172884305622027370793496993281847017017643506435562229916984107083951938286577012273222191422054315198157936674247934699496471202544270325061352014830137178245082445717253260177560449757186762445707057028987371278573629077370632470496186218574320801798046510846708620502139560277546345198686675095078255875594169064796673074708822106659920187882062247609587560174781170641367430722951002242213604709887062481149928551745163110045572994991844223216663621203042075294195007458339984527333125093390189721042315604498435269143549420166732177200370228527273606218617171975362431824163269672003982537382982066136613799403024924018145511099557720492305303748099327810811511080314262364010281851651151072957475365629128068033597559560186625877942054704386175359499573139930378099420149452745731809033737756051947913924265484582800618244473333957173960222243311738522875022546610298627492222587971756897328087719407454153248557203886421828643453889090192355970705084245312184441674098515659253482621260617211786550204852895652236768886852209506535523414991099331857674826373947830587028494510697603296607361093480842935154672353288419699354739650168309017848485131553416956405911683526896232046773861961911767319373432460217755874481607587604361758089936007730253450733375831228127106295259261723611771334468553746160739548375950046831923765023329346333968732796413192682936767133122325481273354810124729664400173367781325488656859581438769940474229394692089519981810909719628263357284973442177568041416363386891516725592952892168077523560584005586276794967492051823290615767599202657060820223928678900774601616908031321346819422162123048834532926372862962159255934240435694566497798544870186550219886342379298214007368081326725550763589917206162393892085506551547475259270513853987294911388226039365971184089828739349642347312302559286882065147953715607221387657413593069535573044067517274676745306396611760657091792151803798859781616126637075577936361782593546481811651450365118155866449850474140044293772144065341051900055416408240857348697564252386403719942197789892382627153382011984996644288495699209129097948405810551134169739499539470610790009272281731894550593600643079188663110695127017324336488487580799309995227054576681630676222848231145106058050452439356753552872060820230589152143268436210090733908507724084889788244157692417246691477400856716677564609725979550100138132944851304473466485128295568194188600539248624248078558656162635444219199062786468487219220160009464328883337821175254405764395407405891483810757405446047244460754827113527540703326714751461178900155717130399854358953609995319006890674085682111514072508440632941090209366005504352890092326935445829213294943731517698438648298921337375443947066950275955144209037675013663600062205168551851984361951824731229113379464426979717688372371011461890139087487634586087688796134318950140718824105959727161482389914414206768064990410615468858520426399188835467970981786227122743162945627167772066100574532803061925537235491026486409948728571706557098859331941260622260924660292578136091523126589085799981416326395824628987154802653126685882440760385315869346960183809644486238810912663304360284449610976505715001267334297285036791711464142665122000857666018757370925847113798258537503747803972255591351740843663253694303946089997282812556281486820325652814785261116697261899511762129550421005941055852897451832731304151488058522478260009347144486599715629242208891126238083949281490804191584238425634093683587199278186505945727829025071885767559828670803412582690901456978557379916793144695491189633486065077294485660840922713748873840986104486221528464294334436081663106336911265802650605150347413103936140565054608396116572669757269475369570465915381045895991937087068526458273755454602799814909213983801968791431574508976448235055061998715636460946550584682626461010298101802277643570201189324102499951196290880892383380284543173390448406975616650185808619832614403133944687275834716343817926764699295672501869876060896683204343897481630037607159476461359111190545646447421653872016775582115425356868533678655969328210255235050133718364831289991244684695035034122861927276046255405376531096051541299607470934463981741370397268760811035606321455156217990078359217247117349544774085111287345436916077577032709684005131011429476229617901273007027774182864475737502587896225475248267937497254066190335088823904767397814233350286976811901982274477445433872253983823904938249655089770642137858608313524715533520654523880832056453080193644871440738737277389718589793074725139142291918837706550037934799585495183374639955887618135803388399608755212147742199481865453122900714456703147150994585431640652462593333773031385396586933380738103697887063571042512186708015948688088011290197524699274772775288900864690592106393483764109837848793374117655194139018455509931621247697015323332300969105814058088442693320033876473960017819576425062784644138417943454576404265382986995583045527928832

Answer 17

Python 2, A000045 (Cracked)

l:= input(a,forge)[]

^{it contains a whitespace and a newline}
Try it Online!
Intended solution

Answer 18

R, A000142, (Cracked)

Byte set:

-()*,`=cfinotu

Intended solution:

f=function(n,c=n==n)'if'(n,f(n-(n==n),c*n),c*(n==n))

Answer 19

cQuents, A000027, Cracked

 !"#%&'()*+,-./0123456789:;?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

That's right! You get all of ASCII! Wait... there's no $... what's $ again in cQuents? Oh, yeah, the index builtin. Well, tough luck :/

Intended Solution:

#|A:A

Try it online!

Answer 20

CJam, A000042, cracked by Lynn

Byte set:

{})_%si

Answer 21

Ruby, A000004, 5 bytes, Cracked

Just messing around to start off. Should be easy for anyone familiar with Ruby. It's a low score, but whatever.

/np.$

---

Cracked, unintended exploit

Cracked (intended answer using n flag)

Answer 22

Python 3, A007504 (Cracked)

This byteset, including newline:

bfuwo)nm1h[=(t+;0a
sig%pr, le:]

My code does not provide infinite output, but can compute the entire b-list.

Answer 23

R, A000290, (cracked)

Byte set:

()%cfinotu

Answer 24

Snowman, 212 bytes, A000042

#$%&*01:;=?@CEFGHIJLMOQUVXYZbcdefghijlmnopqsuvxyz~

... plus space, 0x00-0x1f inclusive, and 0x7f-0xff inclusive.

Answer 25

cQuents, A000217, Cracked

Byteset:

$:=1;
\-

Note that this uses a feature that I haven't pushed the documentation for yet, so I'll push that tonight, if you wait until then. (Or you can slop through my source code... have fun). Documentation pushed. Would be a byte less if a recent bugfix was on TIO.

Intended solution:

=1-1:--\1$ ;$

Try It Online!

Answer 26

JavaScript (ES6), 13 10 bytes, A000045, Cracked

This should be easy.

This is the Fibonacci sequence: F(n) = F(n-1) + F(n-2) with F(0) = 0 and F(1) = 1.

Byte set:

$()-:<=>?[]_~

Edit:

It can be even done with the following 10 bytes:

$()-:=>?_~

Answer 27

R, A105311, (Cracked)

Byte set:

'%(),:=acdegilnopstx

Answer 28

Python3, A008615, Cracked

Bytemap (with newline):

n)ir=-
(u0*pt

Answer 29

Befunge, A000142, 29 Bytes, (Cracked)

Byte Set: @.$_ ^*:\v>-1&

If you can't tell, that Byte set includes a space.

This should be moderately easy to solve.

Edit: Forgot the "A" before the OEIS

Answer 30

R, A105311, (cracked)

'%(),:=acdeginpstx

Let's try this without the l or o.

Since this has been cracked, the intended solution:

cat(diag(diag((a=scan()))%x%diag((a==a):a)),sep=''). diag is an interesting function, that can be used in three different ways. When presented with a single integer (diag(n)), it creates a NxN matrix with 1 on the diagonal. When presented with a vector (diag(1:n)), it creates an NxN matrix with the vector on the diagonal. When presented with a matrix (diag(diag(n))), it returns the diagonal as a vector. %x% computed the Kronecker product of two matrices, where each element in matrix 1 is multiplied with each element in matrix 2 separately. Doing this with a length n identity matrix and a 1:n diagonal matrix, creates a length n^2 diagonal matrix with 1:n repeated n times. diag extracts that again, and cat prints.