OFFSET
1,1
COMMENTS
This is the periodic part of A177904 - it is periodic with period 212.
A smaller start is a(1)=3, a(2)=13, a(3)=7, but that would not produce the terms in the order of their first appearance in A177904.
There are several open questions concerning this class of sequences - see the Back-Caragiu reference in A177904.
LINKS
N. J. A. Sloane, Table of n, a(n) for n = 1..212
MATHEMATICA
nxt[{a_, b_, c_}]:={b, c, FactorInteger[a+b+c][[-1, 1]]}; NestList[nxt, {19, 13, 37}, 120][[All, 1]] (* Harvey P. Dale, Dec 11 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Dec 18 2010
STATUS
approved