%I #18 Jun 13 2018 09:16:14
%S 205,451,529,559,697,1105,1247,1441,1541,1763,1765,1807,1891,1921,
%T 1991,2465,2665,5371,5611,5977,6001,7345,7421,8041,8749,9773,10585,
%U 10621,11041,12167,12403,13333,13981,14473,14491,14981,15457,17611,18721,22399
%N Pseudoprimes to base 42.
%C Composite numbers n such that 42^(n-1) == 1 (mod n). - _Michel Lagneau_, Feb 18 2012
%H T. D. Noe, <a href="/A020170/b020170.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 = 42; 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_