A020209 - OEIS

A020209

Pseudoprimes to base 81.

4, 8, 10, 16, 20, 28, 40, 52, 70, 80, 85, 91, 112, 121, 130, 176, 190, 205, 208, 232, 280, 286, 292, 364, 370, 451, 496, 511, 520, 532, 616, 671, 697, 703, 730, 742, 910, 946, 949, 965, 976, 1036, 1105, 1168, 1261, 1288, 1387, 1435, 1456, 1541, 1606, 1729, 1891

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OFFSET

1,1

COMMENTS

Composite numbers n such that 81^(n-1) == 1 (mod n).

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

Index entries for sequences related to pseudoprimes

MATHEMATICA

base = 81; t = {}; n = 1; While[Length[t] < 100, n++; If[! PrimeQ[n] && PowerMod[base, n-1, n] == 1, AppendTo[t, n]]]; t (* T. D. Noe, Feb 21 2012 *)

CROSSREFS

Cf. A001567 (pseudoprimes to base 2).