A129495 Composite numbers k such that 5^k (mod k) is a power of 5 greater than 1.

10, 15, 20, 26, 30, 34, 38, 40, 46, 50, 56, 58, 60, 62, 65, 74, 78, 82, 86, 94, 100, 106, 118, 120, 122, 124, 129, 130, 132, 134, 140, 141, 142, 143, 146, 150, 155, 158, 159, 166, 177, 178, 182, 183, 190, 194, 195, 200, 201, 202, 206, 213, 214, 217, 218, 219

Offset: 1

Author

Robert G. Wilson v, Apr 17 2007

Keywords

• easy
• nonn

Examples

			26 is a member of the sequence since 5^26 (mod 26) == 25.
		

Links

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

Crossrefs

Cf. A036236, A129492, A129493, A129494, A129496, A129497.

Programs

Mathematica

Select[Range@ 225, (p = PowerMod[5, #, #]) > 1 && IntegerQ@ Log[5, p] && CompositeQ[#] &] (* corrected by Amiram Eldar, Jul 24 2021 *)