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%I #20 Jun 13 2018 09:15:30
%S 9,27,49,81,169,237,301,333,481,553,561,637,711,891,1221,1377,1557,
%T 1729,1813,1891,2107,2133,2553,2821,2871,2997,3321,3397,3439,3537,
%U 3577,3871,3913,5461,6253,6399,6401,6533,6601,6697,7107,7189,7613,7821,8261,8281
%N Pseudoprimes to base 80.
%C Composite numbers n such that 80^(n-1) == 1 (mod n). - _Michel Lagneau_, Feb 18 2012
%H T. D. Noe, <a href="/A020208/b020208.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 = 80; 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[10000],!PrimeQ [#]&&PowerMod[80,#-1,#]==1&] (* _Harvey P. Dale_, Nov 20 2013 *)
%Y Cf. A001567 (pseudoprimes to base 2).
%K nonn
%O 1,1
%A _David W. Wilson_
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