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A256517 Let c be the n-th composite number. Then a(n) is the smallest base b > 1 such that b^(c-1) == 1 (mod c^2), i.e., such that c is a 'Wieferich pseudoprime'. 8
17, 37, 65, 80, 101, 145, 197, 26, 257, 325, 401, 197, 485, 577, 182, 677, 728, 177, 901, 1025, 485, 1157, 99, 1297, 1445, 170, 1601, 1765, 1937, 82, 2117, 2305, 1047, 2501, 577, 529, 2917, 1451, 3137, 721, 3365, 3601, 3845, 244, 4097, 99, 1945, 4625, 530 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Felix Fröhlich, Table of n, a(n) for n = 1..3000

MATHEMATICA

c = Select[Range@ 69, CompositeQ]; f[c_] := Block[{b = 2}, While[Mod[b^(c - 1), c^2] != 1, b++]; b]; f /@ c (* Michael De Vlieger, Apr 03 2015 *)

PROG

(PARI) forcomposite(c=1, 1e3, b=2; while(Mod(b, c^2)^(c-1)!=1, b++); print1(b, ", "))

CROSSREFS

Cf. A039678, A242742, A244752, A255885.

Sequence in context: A269788 A146348 A050952 * A323603 A200865 A319245

Adjacent sequences:  A256514 A256515 A256516 * A256518 A256519 A256520

KEYWORD

nonn

AUTHOR

Felix Fröhlich, Apr 01 2015

STATUS

approved

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Last modified July 8 08:08 EDT 2020. Contains 335520 sequences. (Running on oeis4.)