%I #18 Jun 13 2018 09:16:08
%S 21,49,51,119,133,147,231,301,357,561,637,697,793,817,833,861,931,
%T 1037,1281,1649,1729,2009,2041,2047,2107,2499,2501,2701,2821,2989,
%U 3201,3281,3913,3977,4753,5461,5719,6601,7693,7701,8041,8113,8911,9061,9073,9331
%N Pseudoprimes to base 50.
%C Composite numbers n such that 50^(n-1) == 1 (mod n). - _Michel Lagneau_, Feb 18 2012
%H T. D. Noe, <a href="/A020178/b020178.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 = 50; 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_