A055550 Number of Poulet numbers (or pseudoprimes to base 2, A001567) less than 10^n.

0, 0, 3, 22, 78, 245, 750, 2057, 5597, 14884, 38975, 101629, 264239, 687007, 1801533, 4744920, 12604009, 33763684, 91210364

Offset: 1

Author

Eric W. Weisstein

Keywords

• nonn
• more

References

• J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 245, pp 68, Ellipses, Paris 2008. - Lekraj Beedassy, Jul 20 2008
• Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag NY 2004. See p. 219.

Links

• Jan Feitsma and William Galway, Tables of pseudoprimes and related data.
• Eric Weisstein's World of Mathematics, Poulet Number.
• Eric Weisstein's World of Mathematics, Pseudoprime.

Crossrefs

Cf. A001567, A055552.

Programs

Mathematica

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

Extensions

a(14) and a(15) computed by William F. Galway and communicated by Arthur Livingstone (arthur.livingstone(AT)gmail.com), Apr 10 2007

Edited by N. J. A. Sloane, Feb 01 2009 at the suggestion of Charles R Greathouse IV

a(14)-a(15) recomputed (were missing) and a(16)-a(19) added by Charles R Greathouse IV, Jan 28 2011, based on the calculations of Jan Feitsma