A015921 Positive integers n such that 2^n == 4 (mod n).

1, 2, 4, 6, 10, 12, 14, 22, 26, 30, 34, 38, 46, 58, 62, 74, 82, 86, 94, 106, 118, 122, 132, 134, 142, 146, 158, 166, 170, 178, 182, 194, 202, 206, 214, 218, 226, 254, 262, 274, 278, 298, 302, 314, 326, 334, 346, 358, 362, 372, 382, 386, 394, 398, 422, 446

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Comments

Odd terms are given by A173572.

For all m, 2^A050259(m)-1 belongs to this sequence.

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000
• OEIS Wiki, 2^n mod n

Crossrefs

Contains A050990 as a subsequence.

Cf. A015910, A173572.

Programs

Mathematica

Select[Range[500], PowerMod[2, #, #] == 4 &] (* Alonso del Arte, Jul 07 2011 *)

Extensions

Edited and terms 1,2,4 prepended by Max Alekseyev, Jul 29 2011