A013322 - OEIS

%I #16 Apr 05 2015 11:02:35

%S 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,

%T 28,28,28,36,36,36,36,36,36,36,36,36,36,45,45,45,45,45,45,45,45,45,45,

%U 55,55,55,55,55,55,55,55,55,55,66,66,66,66,66,66,66,66,66,66,66,66

%N Golomb-type sequence over triangular numbers.

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

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

%C The apparent idempotence, a(a(n))=a(n), holds while n<191 and breaks after that. - _Ivan Neretin_, Apr 03 2015

%H Ivan Neretin, <a href="/A013322/b013322.txt">Table of n, a(n) for n = 1..10000</a>

%p A:= 1,3,3,3:

%p for n from 4 to 30 do

%p   t:= n*(n-1)/2;

%p   A:= A, t$A[n-1]

%p od:

%p A; # _Robert Israel_, Apr 03 2015

%t 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 *)

%Y Cf. A001462.

%K nonn,easy

%O 1,2

%A _N. J. A. Sloane_