login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A055550 Number of Poulet numbers (or pseudoprimes to base 2, A001567) less than 10^n. 4
0, 0, 3, 22, 78, 245, 750, 2057, 5597, 14884, 38975, 101629, 264239, 687007, 1801533, 4744920, 12604009, 33763684, 91210364 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

REFERENCES

J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 245, pp 68, Ellipses, Paris 2008. - Lekraj Beedassy, Jul 20 2008

LINKS

Table of n, a(n) for n=1..19.

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

MATHEMATICA

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

CROSSREFS

Cf. A001567, A055552.

Sequence in context: A005288 A143166 A268792 * A075204 A106150 A135836

Adjacent sequences:  A055547 A055548 A055549 * A055551 A055552 A055553

KEYWORD

nonn,more

AUTHOR

Eric W. Weisstein

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

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 27 21:52 EDT 2020. Contains 334671 sequences. (Running on oeis4.)