A013322 Golomb-type sequence over triangular numbers.

1, 3, 3, 3, 6, 6, 6, 10, 10, 10, 15, 15, 15, 15, 15, 15, 21, 21, 21, 21, 21, 21, 28, 28, 28, 28, 28, 28, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66

Offset

1,2

Comments

All terms are triangular numbers; a(n) is length of n-th run.

It is understood that a(n) is taken to be the smallest number >= a(n-1) which is compatible with the description.

The apparent idempotence, a(a(n))=a(n), holds while n<191 and breaks after that. - Ivan Neretin, Apr 03 2015

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Maple

A:= 1, 3, 3, 3:
for n from 4 to 30 do
  t:= n*(n-1)/2;
  A:= A, t$A[n-1]
od:
A; # Robert Israel, Apr 03 2015

Mathematica

a = {1, 3, 3, 3}; Do[a = Join[a, Array[i(i+1)/2&, a[[i]]]], {i, 3, 11}]; a (* Ivan Neretin, Apr 03 2015 *)

Crossrefs

Cf. A001462.

Sequence in context: A057944 A281258 A080607 * A211534 A219816 A177821

Adjacent sequences: A013319 A013320 A013321 * A013323 A013324 A013325

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved