%I #16 Aug 03 2014 14:01:11
%S 4,8,14,25,28,56,65,125,145,203,217,325,377,451,721,725,781,1001,1105,
%T 1625,1885,1891,2047,2296,2465,2701,2821,2911,3193,3277,3565,3625,
%U 3976,4141,4187,5365,5425,6461,6533,6601,7501,7613,8029,8401,9373,9425,10325
%N Pseudoprimes to base 57.
%C Composite numbers n such that 57^(n-1) == 1 (mod n).
%H T. D. Noe, <a href="/A020185/b020185.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>
%t base = 57; 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 *)
%o (PARI) isA020185(n) = (Mod(57,n)^(n-1)==1) && (!isprime(n))
%Y Cf. A001567 (pseudoprimes to base 2).
%K nonn
%O 1,1
%A _David W. Wilson_