login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A118382 Primitive Orloj clock sequences; row n sums to 2n-1. 7
1, 1, 2, 1, 2, 2, 1, 2, 3, 1, 1, 2, 3, 3, 1, 2, 1, 2, 4, 1, 1, 1, 1, 3, 2, 2, 3, 1, 2, 3, 4, 3, 2, 1, 1, 1, 1, 2, 4, 1, 4, 2, 1, 1, 1, 3, 1, 2, 1, 5, 2, 2, 1, 2, 3, 1, 3, 3, 2, 6, 1, 2, 2, 1, 3, 1, 3, 2, 5, 1, 1, 1, 1, 2, 2, 1, 4, 1, 4, 1, 4, 1, 4, 1, 2, 3, 3, 1, 2, 3, 3, 3, 3, 3, 1, 2, 1, 2, 1, 1, 2, 5, 1, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

An Orloj clock sequence is a finite sequence of positive integers that, when iterated, can be grouped so that the groups sum to successive natural numbers. There is one primitive sequence whose values sum to each odd m; all other sequences can be obtained by repeating and refining these. Refining means splitting one or more terms into values summing to that term. The Orloj clock sequence is the one summing to 15: 1,2,3,4,3,2, with a beautiful up and down pattern.

These are known in some papers as Sindel sequences. It appears that this sequence was submitted prior to the first such publication.

LINKS

Table of n, a(n) for n=1..105.

Michal Krížek, Alena Šolcová and Lawrence Somer, Construction of Šindel sequences, Comment. Math. Univ. Carolin., 48 (2007), 373-388.

FORMULA

Let b(i),0<=i<k be all the residues of triangular numbers modulo n in order, with b(k)=n. The differences b(i+1)-b(i) are the sequence for n.

EXAMPLE

For a sum of 5, we have 1,2,2, which groups as 1, 2, 2+1, 2+2, 1+2+2, 1+2+2+1, .... This could be refined by splitting the second 2, to give the sequence 1,2,1,1; note that when this is grouped, the two 1's from the refinement always wind up in the same sum.

The array starts:

  1;

  1,2;

  1,2,2;

  1,2,3,1;

  1,2,3,3;

  1,2,1,2,4,1;

  ...

PROG

(PARI) {Orloj(n) = local(found, tri, i, last, r); found = vector(n, i, 0); found[n] = 1; tri = 0; for(i = 1, if(n%2==0, n-1, n\2), tri += i; if(tri >= n, tri -= n); found[tri] = 1); last = 0; r = []; for(i = 1, n, if(found[i], r = concat(r, [i-last]); last = i)); r}

CROSSREFS

Cf. A028355, A118383. Length of row n is A117484(2n-1) = A000224(2n-1).

Sequence in context: A014643 A236265 A238645 * A007723 A067437 A242425

Adjacent sequences:  A118379 A118380 A118381 * A118383 A118384 A118385

KEYWORD

nonn,tabf

AUTHOR

Franklin T. Adams-Watters, Apr 26 2006

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 1 19:32 EDT 2020. Contains 334762 sequences. (Running on oeis4.)