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A260531 a(n) = (2^p+1)^(p-1) modulo p^2, where p is prime(n). 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

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

LINKS

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

FORMULA

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

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 *)

PROG

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

CROSSREFS

Cf. A000040, A098640, A260507.

Sequence in context: A040459 A040460 A040461 * A252939 A132166 A092083

Adjacent sequences:  A260528 A260529 A260530 * A260532 A260533 A260534

KEYWORD

nonn

AUTHOR

Felix Fröhlich, Jul 28 2015

STATUS

approved

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Last modified July 1 11:09 EDT 2022. Contains 354972 sequences. (Running on oeis4.)