A114248 Number of Fermat pseudoprimes to bases 2, 3 and 5 less than 10^n.

0, 0, 0, 4, 11, 36, 95, 257, 685, 1747, 4405, 10601, 25991, 63589, 156965, 387971, 973753, 2471133, 6340799

Offset: 1

Author

Eric W. Weisstein, Nov 18 2005

Keywords

• nonn
• more

Links

• Eric Weisstein's World of Mathematics, Fermat Pseudoprime.
• Index entries for sequences related to pseudoprimes.

Crossrefs

Cf. A083737.

Programs

Mathematica

Table[Count[Select[Range[2, 10^6], ! PrimeQ[#] && PowerMod[2, # - 1, #] == 1 && PowerMod[3, # - 1, #] == 1 && PowerMod[5, # - 1, #] == 1 &], x_ /; x < 10^n], {n, 6}]  (* Robert Price, Jun 09 2019 *)

Extensions

a(9)-a(19) from Amiram Eldar, Apr 16 2022