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 A137666 Largest prime factor of A137664(n) = (p + 1)^p - 1 for p = prime[n]. 3

%I

%S 2,7,311,337,266981089,29914249171,7563707819165039903,192696104561,

%T 58769065453824529,847499019384726257346113954958447091,

%U 18158209813151,138233050898929517126243814850350442620694127

%N Largest prime factor of A137664(n) = (p + 1)^p - 1 for p = prime[n].

%C 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.

%H Jens Kruse Andersen, <a href="/A137666/b137666.txt">Table of n, a(n) for n = 1..26</a>

%t FactorInteger[#][[-1,1]]&/@((#+1)^#-1&/@Prime[Range[12]]) (* _Harvey P. Dale_, Apr 07 2018 *)

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

%K hard,nonn

%O 1,1

%A _Alexander Adamchuk_, Feb 04 2008

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Last modified November 25 20:42 EST 2020. Contains 338627 sequences. (Running on oeis4.)