A133378 a(1)=1. For n >= 2, a(n) = the largest prime divisor of (a(n-1)^a(n-1) + 1).

1, 2, 5, 521

Offset: 1

Author

Leroy Quet, Oct 28 2007

Keywords

• more
• nonn

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.

Crossrefs

Cf. A007571.

Programs

Mathematica

NestList[FactorInteger[#^#+1][[-1,1]]&,1,3] (* Harvey P. Dale, Jun 21 2012 *)