login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A020145 Pseudoprimes to base 17. 2
4, 8, 9, 16, 45, 91, 145, 261, 781, 1111, 1228, 1305, 1729, 1885, 2149, 2821, 3991, 4005, 4033, 4187, 4912, 5365, 5662, 5833, 6601, 6697, 7171, 8481, 8911, 10585, 11476, 12403, 12673, 13333, 13833, 15805, 15841, 16705, 19345, 19729, 20591, 21781, 22791 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

According to Karsten Meyer, May 16 2006, 4, 8, 9 and 16 should be excluded, following the strict definition in Crandall and Pomerance.

REFERENCES

R. Crandall and C. Pomerance, "Prime Numbers - A Computational Perspective", Second Edition, Springer Verlag 2005, ISBN 0-387-25282-7 Page 132 (Theorem 3.4.2. and Algorithm 3.4.3)

Composite numbers n such that 17^(n-1) == 1 (mod n).

LINKS

R. J. Mathar and T. D. Noe, Table of n, a(n) for n = 1..1000 (R. J. Mathar to 799 terms)

F. Richman, Primality testing with Fermat's little theorem

Index entries for sequences related to pseudoprimes

MATHEMATICA

base = 17; 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 *)

Select[Range[23000], !PrimeQ[#]&&PowerMod[17, #-1, #]==1&] (* Harvey P. Dale, Apr 20 2019 *)

CROSSREFS

Cf. A001567 (pseudoprimes to base 2).

Sequence in context: A089042 A227243 A272575 * A202271 A162898 A257009

Adjacent sequences:  A020142 A020143 A020144 * A020146 A020147 A020148

KEYWORD

nonn

AUTHOR

David W. Wilson

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 June 24 09:37 EDT 2019. Contains 324323 sequences. (Running on oeis4.)