A020211 - OEIS

%I #15 Apr 09 2023 16:36:25

%S 21,65,82,105,123,133,205,231,265,273,287,451,533,561,689,697,703,861,

%T 1001,1105,1113,1241,1365,1558,1729,1785,1891,2173,2465,2569,2665,

%U 2821,2993,3034,3277,3445,4081,4305,4411,4505,4641,4745,5565,5713,6541,6601

%N Pseudoprimes to base 83.

%C Composite numbers n such that 83^(n-1) == 1 (mod n).

%H T. D. Noe, <a href="/A020211/b020211.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 = 83; 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[7000],CompositeQ[#]&&PowerMod[83,#-1,#]==1&] (* _Harvey P. Dale_, Apr 09 2023 *)

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

%K nonn

%O 1,1

%A _David W. Wilson_