A129497 Composite numbers k such that 7^k (mod k) is a power of 7 greater than 1.

14, 21, 25, 42, 50, 56, 58, 62, 70, 74, 82, 84, 86, 94, 98, 105, 106, 112, 118, 122, 132, 133, 134, 142, 146, 147, 150, 152, 158, 166, 168, 178, 182, 194, 196, 202, 206, 210, 214, 218, 226, 231, 254, 262, 266, 274, 278, 294, 298, 301, 302, 314, 325, 326, 334

Offset: 1

Author

Robert G. Wilson v, Apr 17 2007

Keywords

• easy
• nonn

Examples

			58 is a member of the sequence since 7^58 (mod 58) == 49.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A036236, A129492, A129493, A129494, A129495, A129496.

Programs

Mathematica

Select[Range@ 335, (p = PowerMod[7, #, #]) > 1 && IntegerQ@ Log[7, p] && CompositeQ[#] &] (* corrected by Amiram Eldar, Jul 24 2021 *)

Extensions

Corrected and edited by R. J. Mathar, May 16 2008