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%I #21 Aug 22 2017 09:38:17
%S 6,9,15,18,45,49,153,169,343,561,637,889,905,906,1035,1105,1629,1661,
%T 1849,1891,2353,2465,2701,2821,2955,3201,4033,4681,5461,5466,5713,
%U 6223,6541,6601,6697,7957,8145,8281,8401,8869,9211,9997,10021,10515,10585
%N Pseudoprimes to base 19.
%C According to _Karsten Meyer_, May 16 2006, 6, 9 and 18 should be excluded, following the strict definition in Crandall and Pomerance.
%C Composite numbers n such that 19^(n-1) == 1 (mod n).
%D R. Crandall and C. Pomerance, "Prime Numbers - A Computational Perspective", Second Edition, Springer Verlag 2005, ISBN 0-387-25282-7 Page 132 (Theorem 3.4.2. and Algorithm 3.4.3)
%H R. J. Mathar, <a href="/A020147/b020147.txt">Table of n, a(n) for n = 1..1000</a>
%H F. Richman, <a href="http://math.fau.edu/Richman/carm.htm">Primality testing with Fermat's little theorem</a>
%H <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>
%t base = 19; 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_
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