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A178813 (Prime(n)^(p-1) - 1)/p^2 mod p, where p is the first prime that divides (prime(n)^(p-1) - 1)/p. 2
487, 4, 1, 1, 46, 1, 0, 1, 11, 1, 2, 1, 0, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

(Prime(n)^(p-1) - 1)/p^2 mod p, where p = A174422(n) is the first Wieferich prime base prime(n).

(Prime(n)^(p-1) - 1)/p^2 mod p, where p is the first prime such that p^2 divides prime(n)^(p-1) - 1.

See references and additional comments, links, and cross-refs in A001220 and A039951.

LINKS

Table of n, a(n) for n=1..14.

Wikipedia, Generalized Wieferich primes

FORMULA

a(n) = k mod 2, if prime(n) = 4k+1.

a(n) = A178814(prime(n)) .

a(1) = A178812(1).

EXAMPLE

Prime(2) = 3 and the first prime p that divides (3^(p-1) - 1)/p is 11, so a(2) = (3^10 - 1)/11^2 mod 11 = 488 mod 11 = 4.

CROSSREFS

Cf. A001220, A039951, A174422, A178812, A178814.

Sequence in context: A097765 A179428 A252076 * A178814 A178812 A124667

Adjacent sequences:  A178810 A178811 A178812 * A178814 A178815 A178816

KEYWORD

hard,more,nonn

AUTHOR

Jonathan Sondow, Jun 17 2010

STATUS

approved

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Last modified December 11 02:17 EST 2019. Contains 329910 sequences. (Running on oeis4.)