A020196 - OEIS

%I #23 Jun 25 2018 03:47:48

%S 25,49,69,91,125,133,185,201,217,247,325,345,361,403,469,481,589,637,

%T 805,871,925,931,1005,1025,1221,1225,1273,1417,1519,1541,1725,1729,

%U 1771,1813,2077,2185,2211,2413,2527,2553,2665,2725,2821,3283,3325,3565,4033,4123

%N Pseudoprimes to base 68.

%C Composite numbers n such that 68^(n-1) == 1 (mod n). - _Michel Lagneau_, Feb 18 2012

%H T. D. Noe, <a href="/A020196/b020196.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 max = 5000; Select[Complement[Range[max], Prime[Range[PrimePi[max]]]], PowerMod[68, # - 1, #] == 1 &] (* _Alonso del Arte_, Jun 17 2018 *)

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

%K nonn

%O 1,1

%A _David W. Wilson_