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

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A020168 Pseudoprimes to base 40. 1
39, 91, 121, 123, 289, 451, 533, 561, 703, 793, 1541, 1561, 1599, 1729, 1921, 2821, 2899, 3097, 3367, 3751, 3829, 4961, 5461, 5729, 6031, 6601, 7111, 7201, 7381, 8911, 9073, 9881, 10897, 11011, 11041, 11121, 11521, 12403, 12801, 13073, 13333, 13981 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Composite numbers n such that 40^(n - 1) == 1 (mod n). - Michel Lagneau, Feb 18 2012

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

Index entries for sequences related to pseudoprimes

MATHEMATICA

base = 40; pp40 = {}; n = 1; While[Length[pp40] < 100, n++; If[!PrimeQ[n] && PowerMod[base, n - 1, n] == 1, AppendTo[pp40, n]]]; pp40 (* T. D. Noe, Feb 21 2012 *)

searchMax = 10000; Complement[Select[Range[searchMax], PowerMod[40, # - 1, #] == 1 &], Prime[Range[PrimePi[searchMax]]]] (* Alonso del Arte, Feb 20 2020 *)

CROSSREFS

Cf. A001567 (pseudoprimes to base 2).

Sequence in context: A044177 A044558 A242181 * A063318 A039422 A043245

Adjacent sequences:  A020165 A020166 A020167 * A020169 A020170 A020171

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 December 1 21:31 EST 2020. Contains 338858 sequences. (Running on oeis4.)