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I've been really interested with sequences that follow the property

\$a(n+1) = a(n - a(n))\$

recently, so here's another question about these sequences. In particular we are concerned with sequences from the integers to the natural numbers.

A periodic sequence with the above property is an n-Juggler if and only if it contains exactly n distinct values. For example the following sequence is a 2 juggler

... 2,2,1,2,2,1,2,2,1,2,2,1,2,2,1,2,2,1,2,2,1,2,2,1,2,2,1,2,2,1,2,2,1,2,2,1 ...

because it only contains the numbers 1 and 2.

An example of a three juggler would be

... 3,5,3,5,1,5,3,5,3,5,1,5,3,5,3,5,1,5,3,5,3,5,1,5,3,5,3,5,1,5,3,5,3,5,1,5 ...

because it juggles 1, 3, and 5.

Task

Given n > 1 as input, output any n-Juggler.

You may output a sequence in a number of ways, you can

  • output a function that indexes it.

  • take an additional input of the index and output the value at that index.

  • output a continuous subsection of the sequence that, with the given property uniquely determines the sequence.

This is so answers are scored in bytes with less bytes being better.

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    \$\begingroup\$ Are we allowed to print the sequence indefinitely? \$\endgroup\$
    – Mr. Xcoder
    Commented Oct 26, 2017 at 15:31
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    \$\begingroup\$ @Mr.Xcoder Normally I would say yes, but since these sequences are infinite in both directions, I have to hesitantly say no. (If you offer a compelling argument I could easily change my mind on this) If you can find a way to print in both directions that would be fine. \$\endgroup\$
    – Wheat Wizard ♦
    Commented Oct 26, 2017 at 15:33
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    \$\begingroup\$ It seems the sequnces follow a(n+1) = a(n-a(n)), and not + \$\endgroup\$
    – TFeld
    Commented Oct 26, 2017 at 16:05
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    \$\begingroup\$ Yes it does: repeat 2,2 once → 2,2,2,2, repeat again → 2,2,2,2,2,2, etc. There's absolutely no way to get a 1 from repeating 2,2. The sequence you get is always unique. \$\endgroup\$
    – aditsu quit because SE is EVIL
    Commented Oct 26, 2017 at 17:10
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    \$\begingroup\$ It looks like the property is no more. \$\endgroup\$
    – Erik the Outgolfer
    Commented Aug 26, 2018 at 19:24

7 Answers 7

Reset to default
5
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Pyth, 5 bytes

t+*%E

Try the 2, 3, 4 Jugglers.

Receives two numbers, N and I, separated by a newline and in this order. I is the index into the sequence.

This uses a quite simple formula: N - 1 + N * (I % N). Its validity was confirmed by the OP.

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3
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CJam, 9

How about this?

q~1$,=)*(

Try it online

Input is n i where n is the main input and i is the index you want to get the value for.

Explanation:

q~    read and evaluate the input (n and i)
1$    copy n
,=    basically this is a modulo (i%n) that avoids a negative result for negative i
)*    increment, then multiply by n
(     decrement
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1
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Haskell, 17 bytes

n!i=i`mod`n*n+n-1

Try it online!

Another answer using Mr. Xcoder's idea. I wouldn't be able to answer the question otherwise to be honest. :P

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1
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Python 2, 20 bytes

lambda n,i:i%n*n+n-1

Try it online!

Same principle as Mr. Xcoder's answer

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    \$\begingroup\$ Should principal not rather read principle? \$\endgroup\$
    – Jonathan Frech
    Commented Aug 26, 2018 at 20:28
  • \$\begingroup\$ @JonathanFrech... yeah.. \$\endgroup\$
    – TFeld
    Commented Aug 27, 2018 at 6:55
1
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Vyxal, 4 bytes

%›*‹

Try it Online!

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1
  • \$\begingroup\$ without the -1 your function obeys \$a(n)=a(n-a(n))\$. \$\endgroup\$
    – att
    Commented Jun 10, 2022 at 4:14
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Java 8, 15 bytes

n->i->i%n*n+n-1

Boring port of @Mr.Xcoder's Pyth answer.

Try it here.

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0
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Jelly, 5 bytes

Ɠ%×+’

Try it online!

Port of Mr. Xcoder's approach. The index I is in STDIN, N is an argument.

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