A020149 Pseudoprimes to base 21.

4, 10, 20, 55, 65, 85, 221, 703, 793, 1045, 1105, 1852, 2035, 2465, 3781, 4630, 5185, 5473, 5995, 6541, 7363, 8695, 8965, 9061, 10585, 10945, 11647, 13019, 13051, 13981, 14491, 17767, 18103, 18721, 19345, 19669, 19909, 21667, 22681, 23155, 24013, 25465

Offset

1,1

Comments

Composite numbers n such that 21^(n-1) == 1 (mod n).

Links

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

Index entries for sequences related to pseudoprimes

Mathematica

base = 21; 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 *)

Crossrefs

Cf. A001567 (pseudoprimes to base 2).

Sequence in context: A189586 A019498 A237626 * A056412 A032275 A220828

Adjacent sequences: A020146 A020147 A020148 * A020150 A020151 A020152

Keyword

nonn

Author

David W. Wilson

Status

approved