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A074476 Largest prime factor of 3^n + 1. 9
2, 2, 5, 7, 41, 61, 73, 547, 193, 37, 1181, 661, 6481, 398581, 16493, 271, 21523361, 1021, 530713, 101917, 42521761, 2269, 570461, 23535794707, 769, 22996651, 4795973261, 19927, 647753, 5385997, 47763361, 22434744889, 926510094425921 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 0..658 (terms 0..100 from Vincenzo Librandi)

S. S. Wagstaff, Jr., The Cunningham Project

FORMULA

a(n) = A006530(A034472(n)). - Amiram Eldar, Feb 01 2020

MATHEMATICA

Table[FactorInteger[3^n + 1][[-1, 1]], {n, 0, 40}] (* Vincenzo Librandi, Aug 23 2013 *)

PROG

(PARI) for(n=0, 35, v=factor(3^n+1); print1(v[matsize(v)[1], 1], ", "))

(MAGMA) [Maximum(PrimeDivisors(3^n+1)): n in [0..40]]; // Vincenzo Librandi, Aug 23 2013

CROSSREFS

Cf. A006530, A034472, A074477 (largest prime factor of 3^n - 1), A002587 (largest prime factor of 2^n + 1), A074478 (largest prime factor of 5^n + 1).

Sequence in context: A300439 A208818 A221835 * A224610 A265819 A254746

Adjacent sequences:  A074473 A074474 A074475 * A074477 A074478 A074479

KEYWORD

nonn

AUTHOR

Rick L. Shepherd, Aug 23 2002

STATUS

approved

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Last modified December 2 01:48 EST 2020. Contains 338864 sequences. (Running on oeis4.)