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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 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.)