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A133378 a(1)=1. For n >= 2, a(n) = the largest prime divisor of (a(n-1)^a(n-1) + 1). 0
1, 2, 5, 521 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..4.

factordb.com, 521^521+1.

MATHEMATICA

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

CROSSREFS

Cf. A007571.

Sequence in context: A138696 A163798 A081296 * A283561 A037063 A068105

Adjacent sequences: A133375 A133376 A133377 * A133379 A133380 A133381

KEYWORD

more,nonn,changed

AUTHOR

Leroy Quet, Oct 28 2007

STATUS

approved

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Last modified January 28 18:26 EST 2023. Contains 359905 sequences. (Running on oeis4.)