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Pseudoprimes to base 61.
1

%I #13 Aug 03 2014 14:01:12

%S 4,6,10,12,15,20,30,52,60,91,93,130,155,190,217,341,388,403,465,561,

%T 679,786,970,1105,1261,1441,1729,2388,2465,2701,2821,3007,3406,3565,

%U 3661,4061,4123,4371,4577,4580,5044,5356,5461,6541,6601,6697,6799,7107,7372

%N Pseudoprimes to base 61.

%C Composite numbers n such that 61^(n-1) == 1 (mod n).

%H T. D. Noe, <a href="/A020189/b020189.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 = 61; 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_