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

MATL, 11 bytes, A000984

Uses some of these bytes (ASCII):

$&)+/:HZdep

Due to floating-point precision, results are only guaranteed to be accurate up to the 26-th term. I hope that's acceptable.

Answer 2

JavaScript (ES6), 10 bytes, A000007

Byte set: -)$>yRa=A(

Answer 3

Seed, A000027 (Counting Numbers) (Cracked)

You may use any valid character in Seed:

[0-9 ]

Have fun! The resulting Befunge program is short, so you should definitely be able to brute force it within a week (if you're crazy enough to do that).

My Solution:

My solution is a little bit longer than Lynn's solution...

4 47142938850356537668025719950342285215695875470457212766920093958965599014291682211474803930206233718243166021324700185443274842742744297183042397910454208210130742260519105651032450664856693714718759816232968955289663444878636053035645231246428917992493766505872029989544065894418166685284738859999912471659057565000392419689361271972485444731284404987238803115210428572945108908191097214978382112218242627719651728712577306652405452922782307249485947045215982784790396555726144526602778473387279897334709142853151393812930171163300904436548870603006549005515709074682843356844201220668045057407146751793470423217099467145255174198241606814578351260769359571053755888106818197239116973006365593563235361647743411341624822052103816968153274122434280200888824954875622811325064255818154979564925710534165572852442761249176778416688044630942040966271963723430245979221181930857841829694362184653939393940015797332978459794253176110314873994228261888801228999293570329618551223457182420746927212801550646743152754821640064626761542582557138452651970009253770914346130172884305622027370793496993281847017017643506435562229916984107083951938286577012273222191422054315198157936674247934699496471202544270325061352014830137178245082445717253260177560449757186762445707057028987371278573629077370632470496186218574320801798046510846708620502139560277546345198686675095078255875594169064796673074708822106659920187882062247609587560174781170641367430722951002242213604709887062481149928551745163110045572994991844223216663621203042075294195007458339984527333125093390189721042315604498435269143549420166732177200370228527273606218617171975362431824163269672003982537382982066136613799403024924018145511099557720492305303748099327810811511080314262364010281851651151072957475365629128068033597559560186625877942054704386175359499573139930378099420149452745731809033737756051947913924265484582800618244473333957173960222243311738522875022546610298627492222587971756897328087719407454153248557203886421828643453889090192355970705084245312184441674098515659253482621260617211786550204852895652236768886852209506535523414991099331857674826373947830587028494510697603296607361093480842935154672353288419699354739650168309017848485131553416956405911683526896232046773861961911767319373432460217755874481607587604361758089936007730253450733375831228127106295259261723611771334468553746160739548375950046831923765023329346333968732796413192682936767133122325481273354810124729664400173367781325488656859581438769940474229394692089519981810909719628263357284973442177568041416363386891516725592952892168077523560584005586276794967492051823290615767599202657060820223928678900774601616908031321346819422162123048834532926372862962159255934240435694566497798544870186550219886342379298214007368081326725550763589917206162393892085506551547475259270513853987294911388226039365971184089828739349642347312302559286882065147953715607221387657413593069535573044067517274676745306396611760657091792151803798859781616126637075577936361782593546481811651450365118155866449850474140044293772144065341051900055416408240857348697564252386403719942197789892382627153382011984996644288495699209129097948405810551134169739499539470610790009272281731894550593600643079188663110695127017324336488487580799309995227054576681630676222848231145106058050452439356753552872060820230589152143268436210090733908507724084889788244157692417246691477400856716677564609725979550100138132944851304473466485128295568194188600539248624248078558656162635444219199062786468487219220160009464328883337821175254405764395407405891483810757405446047244460754827113527540703326714751461178900155717130399854320238635234164429884664271159504714368008455653061601459723385727262777232764564573673873772208222457183846136405752956618693937985108892893985455752900109747276359722218661153262749015305405756329658744441481575547254529963547290233424398012124166511178581644295375904189900373061373853471489496222876806462541916199940534855562482928962080779491332702863921351256172643450743469939804784306286205587292552998145733381435925702081855362374409244827640579395543246453123597643190692540938806013686596772963034314363354010871521973403725835700408947963387110274004628480425371734331910891935140460595015189156420163115488068088520486798706569490006916112796733633895122682258059129006594304004203161927532260544237735899697152969940248758172957772287759336801595261613720119580891726456931895143417855893848415813470404827691913198395587019754512910027895295524122640301750273229263700158423422494600783294301471077720755163088097928474808200825811331834384330131090616226795924514158947235407965623454021092089105236025774499670509312408897668570458845620423145441557589436789713088947243846896823513743795131462439985465454654508125778329519910755888052092925306512948187971238329609568930378458165199920437525216462470929107070404811453630873763646812061350580161443056020563505260186672704841049972564837245044063297483792279875783885332694312955039151703943626840229495942158368887321883672956326501715270278543111513846830331160757034936022626603927067201550075630055296060821698451711220226998542584472966056248420845670285305975196992649811350779376980410458954534606441616709943508562093877902996409050522302853982991210150961788557227893313889825011281746787557452112185337922107257901043776646541934164147921577497411930472664026894384833716916001510862714001082105916461354489145794983975342462583664139916994875750562786683033654066234795041967161156949148282294752956521537053912878502375506909313842856133697079387338725355753694963250928996068864246591064004864326952187480597051907196284596345012237848475736570739686898404311769576575237233438553293161482584973742517010294566986396986963333792493710800886286588229647009335037917560300340277732774595016553407284174237194411762775063365955286488230300605484062176178336345135677894004813511507360069468591733327248913533084977745451497662084575239380871947004076480854627777980299105041121280

Answer 4

Ruby, A000217, 15 bytes, Cracked

Uses the -p flag to take input from stdin and output to stdout.

$mu.to_vim[d=s]

Intended solution:

$_=[$...$_.to_i][$..div$$].sum

Answer 5

Haskell, A001107 (cracked)

This one is easier, the sequence is growing slower and the charset is smaller.

Compute the decagonal numbers n(4n-3) using the following charset of size 9:

.,_-=[ ]!

Again there is no newline.

Answer 6

C, A000312 (cracked)

-,;:?(){} eglnortu

The specs call for a complete program, however this would add many more characters to the byte set making the challenge trivial. Instead, you’ll be providing the code within this template:

«your-code-composed-of-characters-in-byte-set»

#include <stdlib.h>
#include <stdio.h>

int main(int argc, char** argv)
{
    int n = argc > 1? atoi(argv[1]): 0;
    printf("%d ^ %d = %lld\n", n, n, «your-function-name»(n));
    return 0;
}

Note that your code comes before the #includes.

Answer: long long l(long long o,long long n){return o- -n;} long long o(long long n,long long g){return g?(--g?l(o(n,g),n):n):g;} long long n(long long g,long long l){return l?o(n(g,--l),g):- --l;} long long g(long long l){return n(l,l);} Addition l is expressed as subtraction of a negated value m + n = m − (−n), multiplication o as a series of additions m × n = m × (n − 1) + m, exponentiation n as a series of multiplications mⁿ = mⁿ⁻¹ × m, and finally the function g which calls the exponentiation function. On machines where long long is 64 bits wide, this code will give incorrect answers for n ≥ 16, but note there are machines out there with word lengths of more than 64 bits, e.g. the Ethereum Virtual Machine (EVM) with 256-bit words where long long could naturally accommodate values ≫ 2⁶⁴. So in theory the code would work for n ≥ 16.

Answer 7

CPython 3.6.2, A000720 (cracked)

I have decided to squeeze as many characters out of Latin-1 as possible without simplifying the challenge. There are some unprintables, so I will provide the characters in the following format:

print(",".join((
    "0x0-0x8",
    "0xa-0x1f",  #inc. \n
    "0x23-0x24",  # chars #$
    "0x28-0x29",  # chars ()
    "0x2c",  # char ,
    "0x2e",  # char .
    "0x3b",  # char ;
    "0x3d",  # char =
    "0x3f",  # char ?
    "0x41-0x5d",  # A-Z and chars [\]
    "0x5f",  # char _
    "0x62-0x64", # chars bcd
    "0x69",  # char i
    "0x6c",  # char l
    "0x6e",  # char n
    "0x73-0x75", # chars stu
    "0x7f-0xff"
)))

I think that makes 208 characters. Feel free to use any of these.

I did not hard-code; that would take so many characters I would have to start meta-meta-programming. This set of characters is provably Turing-complete.

Answer 8

Python 2, A005150 (Look and say), safe

 "()+,.01:=ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]_celnortwx

Gee, you don't didn't have much, do did you?

Intended solution:

exec("FROM ITERTOOLS IMPORT GROUPBY\nA=\"1\"\nFOR _ IN RANGE(1,INT(INPUT())):\n\tA=[\"\".JOIN(GRP)FOR M,GRP IN GROUPBY(A)]\n\tA=\"\".JOIN([STR(LEN(X))+X[0]FOR X IN A])\nPRINT(A)".lower()) You have all of the uppercase characters, and just enough lowercase ones for \n, \t, exec and lower.

Answer 9

Perl 5 -p, A005843, score:16, safe.

 .0123456789aelv

A simple problem. You should solve this easily if you are familiar with the language well.

Intended solution

eval 36.95.42.61.50 How it works: version number such as 5.10.3 is represented as a string. So, you just need to construct a version number to be evaluated. Example: v33 is '!'.

Answer 10

CLC-INTERCAL 1.-94.-2, A001477, safe, score: 16.

Byteset:

@ABDEHIP`abdehip

You may use any i/o method. Also you may use any compiler option.

Try it online! Submitting as CLC-INTRCAL does not let you set compiler option, so you might need to try as shell.

The answer

D`h@I@`P@pAB@d@p`DPb@PD`h@`P@d@aD`h@E@ABPb@P

This is equivalent to DOWRITEIN.1DOREADOUT.1 in Hollerith character set; so input range is OH or ZERO to SIX FIVE FIVE THREE FIVE (inclusive).

Try the following Bash script online:

printf 'D`h@I@`P@pAB@d@p`DPb@PD`h@`P@d@aD`h@E@ABPb@P'>.i;sick -h .i;./.io

How it works

The code can be in Hollerith character set. However, it is implemented incorrectly so the code above is for such behaviour as in implementation, not for documentation.

Here is the script to accept punch lines to generate a program in Hollerith.

Also why doesn't the compiler guess anything other than ASCII? So I had to force it to use my intended character code, by -h.

See also

My answer on Print X without X

Answer 11

CLC-INTERCAL, A001477, safe, score: 14.

Byteset:

ACFGIJLPRWX[\_

Rules

• You may use any compiler option.
• You may specify i/o format by yourself.
• You may specify range of input.
• You may specify whether 0-indexed or 1-indexed.
• I made a program that works on this online environment.

Answer

IXRJFPAFL[\W_IXJACIXGP[\W

This is DOWRITEIN.1DOREADOUT.1 in Baudot encoding, so input range is OH or ZERO to SIX FIVE FIVE THREE FIVE. Due to the encoding, you need compiler option -b if it is newer so the character guessing does not work.

Try the following Bash script in online environment

printf %s 'IXRJFPAFL[\W_IXJACIXGP[\W'>.i
sick -b .i
./.io<<<'THREE FOUR FIVE'

Copy and paste to try it online!

See also

• My problem that requires Hollerith encoding
• My problem that requires EBCDIC encoding

Answer 12

Javascript (ES6), A000079, 6 Bytes

[]()+!

Hint:

Intended solution is 25496 characters long.