A020182 - OEIS

%I #20 Jul 03 2019 17:42:06

%S 55,265,341,361,385,583,781,1045,1105,1247,1729,1855,2201,2465,2701,

%T 2821,2863,2915,3445,4033,4069,4081,5005,5317,5461,6095,6601,7471,

%U 7957,8321,8911,9073,10585,11713,13357,14585,14701,14905,15409,15841,17755,18721

%N Pseudoprimes to base 54.

%C Composite numbers n such that 54^(n-1) == 1 (mod n). - _Michel Lagneau_, Feb 18 2012

%H T. D. Noe, <a href="/A020182/b020182.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 = 54; 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[20000],!PrimeQ[#]&&PowerMod[54,#-1,#]==1&] (* _Harvey P. Dale_, Jul 03 2019 *)

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

%K nonn

%O 1,1

%A _David W. Wilson_