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Pseudoprimes to base 91.
1

%I #15 Aug 15 2017 18:00:08

%S 6,9,10,15,18,30,45,66,69,90,115,205,207,341,345,369,435,505,561,909,

%T 1035,1065,1387,1446,1541,1845,2047,2059,2465,2651,2701,2829,2871,

%U 3015,4005,4141,4187,4371,4545,5963,6273,6533,6969,7471,8646,9361,9881,10585

%N Pseudoprimes to base 91.

%C Composite numbers n such that 91^(n-1) == 1 (mod n).

%H T. D. Noe, <a href="/A020219/b020219.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 = 91; 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 *)

%t Select[Range[11000],CompositeQ[#]&&PowerMod[91,#-1,#]==1&] (* _Harvey P. Dale_, Aug 15 2017 *)

%Y Cf. A001567 (pseudoprimes to base 2).

%K nonn

%O 1,1

%A _David W. Wilson_