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A137666 Largest prime factor of A137664(n) = (p + 1)^p - 1 for p = prime[n]. 3
2, 7, 311, 337, 266981089, 29914249171, 7563707819165039903, 192696104561, 58769065453824529, 847499019384726257346113954958447091, 18158209813151, 138233050898929517126243814850350442620694127 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) is also the largest prime factor of A137665(n) = A137664(n)/Prime(n)^2. p^2 divides A137664(n) = (p + 1)^p - 1, p = Prime[n]. Least prime factors of A137664(n) are listed in A128456(n) = {2,7,311,127,23,157,7563707819165039903,...}. a(n) = A128456(n) = A137665(n) = ((p + 1)^p - 1)/p^2 for n = {1,2,3,7,595,...} corresponding to p = Prime(n) = {2,3,5,17,4357,...} = A127837.

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..26

MATHEMATICA

FactorInteger[#][[-1, 1]]&/@((#+1)^#-1&/@Prime[Range[12]]) (* Harvey P. Dale, Apr 07 2018 *)

CROSSREFS

Cf. A128452, A128456, A128356, A128357, A137664, A137665, A128466, A127837.

Sequence in context: A290637 A260967 A128456 * A137665 A128466 A048122

Adjacent sequences:  A137663 A137664 A137665 * A137667 A137668 A137669

KEYWORD

hard,nonn

AUTHOR

Alexander Adamchuk, Feb 04 2008

STATUS

approved

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Last modified February 20 15:04 EST 2019. Contains 320327 sequences. (Running on oeis4.)