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A268352 Second base-n Wieferich prime, i.e., second smallest prime p such that n^(p-1) == 1 (mod p^2). 1
3511, 1006003, 3511, 20771, 534851, 491531, 1093, 11, 487 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Column 2 of table T(n, k) of k-th base-n Wieferich prime for n > 1 (that table is not yet in the OEIS as a sequence).

a(11) is unknown, but must be larger than 1.202*10^13 if it exists (cf. Fischer).

LINKS

Table of n, a(n) for n=2..10.

R. Fischer, Thema: Fermatquotient B^(P-1) == 1 (mod P^2)

EXAMPLE

a(3) = 1006003, because 1006003 is the second smallest prime p satisfying 3^(p-1) == 1 (mod p^2) (see A014127).

PROG

(PARI) a(n) = my(i=0); forprime(p=1, , if(Mod(n, p^2)^(p-1)==1, if(i > 0, return(p), i++)))

CROSSREFS

Cf. A039951, A178871.

Sequence in context: A043448 A281002 A273472 * A178871 A317162 A306174

Adjacent sequences:  A268349 A268350 A268351 * A268353 A268354 A268355

KEYWORD

nonn,hard,more

AUTHOR

Felix Fröhlich, Feb 02 2016

STATUS

approved

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Last modified October 20 01:16 EDT 2018. Contains 316378 sequences. (Running on oeis4.)