OFFSET
1,2
COMMENTS
a(5) depends on the factorization of the 1408-digit composite number (521^521+1)/(2 * 3^2 * 29 * 375121); see factordb.com link. - Michael S. Branicky, Jan 27 2023
LINKS
factordb.com, 521^521+1.
MATHEMATICA
NestList[FactorInteger[#^#+1][[-1, 1]]&, 1, 3] (* Harvey P. Dale, Jun 21 2012 *)
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Leroy Quet, Oct 28 2007
STATUS
approved