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
KEYWORD
nonn,easy
AUTHOR
STATUS
approved