A260531 a(n) = (2^p+1)^(p-1) modulo p^2, where p is prime(n).

1, 0, 21, 1, 45, 79, 120, 305, 484, 697, 404, 186, 1354, 603, 612, 2757, 945, 3051, 3552, 498, 950, 1186, 2657, 1781, 6403, 9192, 8035, 1927, 2181, 2713, 6097, 2621, 10139, 3476, 10878, 8608, 22609, 21028, 24550, 19031, 1, 12852, 33426, 27793, 34279, 11543

Offset: 1

Author

Felix Fröhlich, Jul 28 2015

Keywords

• nonn

Comments

The primes where a(n) == 1 are given by A260507.

Links

• Felix Fröhlich, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A098640, A260507.

Programs

Mathematica

f[n_] := Block[{p = Prime@ n}, PowerMod[2^p + 1, p - 1, p^2]]; Array[f, 46] (* Robert G. Wilson v, Jul 29 2015 *)

PARI

a(n) = lift(Mod(2^prime(n)+1, prime(n)^2)^(prime(n)-1))

Formula

a(n) = A098640(n)^(A000040(n)-1) modulo A000040(n)^2.