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%I #6 Jun 07 2021 01:10:45
%S 8,63,7775,2097151,743008370687,793714773254143,
%T 2185911559738696531967,5242879999999999999999999,
%U 55572324035428505185378394701823,6863037736488299999999999999999999999999999
%N a(n) = (p+1)^p - 1 where p = prime(n).
%C p^2 divides a(n) = (p+1)^p - 1, p = prime(n).
%C Quotients a(n)/prime(n)^2 are listed in A137665(n) = {2, 7, 311, 42799, 6140565047, 4696537119847, 7563707819165039903, ...}.
%C Least prime factors of A137665(n) = a(n)/prime(n)^2 are listed in A128456(n) = {2, 7, 311, 127, 23, 157, 7563707819165039903, ...}.
%C Largest prime factors A137665(n) = a(n)/prime(n)^2 are listed in A137666(n) = {2, 7, 311, 337, 266981089, 29914249171, 7563707819165039903, ...}.
%F a(n) = (prime(n) + 1)^prime(n) - 1.
%t Table[ (Prime[n] + 1)^Prime[n] - 1, {n,1,15} ]
%Y Cf. A128452, A128456, A128356, A128357, A137665, A137666.
%K nonn
%O 1,1
%A _Alexander Adamchuk_, Feb 04 2008
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