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A178812 (2^(p-1) - 1)/p^2 modulo prime p, if p^2 divides 2^(p-1) - 1. 2
487, 51 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

(2^(p-1) - 1)/p^2 modulo p, where p is a Wieferich prime A001220.

(2^(p-1) - 1)/p^2 modulo p, if prime p divides the Fermat quotient (2^(p-1) - 1)/p.

See A001220 for references, links, and additional comments.

LINKS

Table of n, a(n) for n=1..2.

FORMULA

a(n) = (2^(p-1) - 1)/p^2 modulo p, where p = A001220(n).

a(1) = A178813(1).

EXAMPLE

a(1) = 487 as the first Wieferich prime is 1093 and (2^1092 - 1)/1093^2 == 487 (mod 1093).

The 2nd Wieferich prime is 3511 and (2^3510 - 1)/3511^2 == 51 (mod 3511), so a(2) = 51.

CROSSREFS

Cf. A001220, A178813.

Sequence in context: A252076 A178813 A178814 * A124667 A142540 A048424

Adjacent sequences:  A178809 A178810 A178811 * A178813 A178814 A178815

KEYWORD

bref,hard,more,nonn

AUTHOR

Jonathan Sondow, Jun 16 2010

STATUS

approved

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Last modified January 20 19:53 EST 2020. Contains 331096 sequences. (Running on oeis4.)