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Pseudoprimes to base 31.
2

%I #17 Aug 03 2014 14:01:11

%S 6,10,15,30,49,65,66,133,185,451,481,561,637,931,946,1105,1221,1729,

%T 1813,2317,2405,2465,2553,3310,4753,4921,6241,6289,6601,7107,7421,

%U 7449,8177,8911,9073,9131,10470,10585,10963,11041,12403,14191,16219,17767,18721

%N Pseudoprimes to base 31.

%C Composite numbers n such that 31^(n-1) == 1 (mod n).

%H R. J. Mathar and T. D. Noe, <a href="/A020159/b020159.txt">Table of n, a(n) for n = 1..1000</a> (R. J. Mathar 837 terms)

%H <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>

%t base = 31; 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 *)

%Y Cf. A001567 (pseudoprimes to base 2).

%K nonn

%O 1,1

%A _David W. Wilson_