A020169 Pseudoprimes to base 41.

4, 8, 10, 15, 20, 21, 35, 40, 105, 145, 231, 344, 561, 609, 645, 671, 703, 841, 1065, 1105, 1281, 1387, 1417, 1729, 1885, 1891, 2121, 2465, 2701, 2821, 3045, 3053, 3829, 4033, 4205, 4521, 4870, 5365, 5565, 6161, 6892, 7957, 8295, 8321, 8695, 8905, 8911, 9253

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

Composite numbers n such that 41^(n-1) == 1 (mod n).

Links

• R. J. Mathar, Table of n, a(n) for n=1..1003
• Index entries for sequences related to pseudoprimes

Crossrefs

Cf. A001567 (pseudoprimes to base 2).

Programs

Magma

[n: n in [1..3*10^4] | IsOne(Modexp(41, n-1, n)) and not IsPrime(n)]; // Vincenzo Librandi, Mar 15 2019

Mathematica

base = 41; 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 *)