A277187 Numbers n such that A001158(n) == 1 (mod n).

2, 3, 4, 5, 7, 8, 9, 11, 13, 17, 19, 23, 25, 27, 29, 31, 36, 37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 121, 125, 127, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 289, 293

Offset: 1

Author

Ilya Gutkovskiy, Oct 04 2016

Keywords

• nonn
• easy

Comments

Essentially the same as A087797. - Ilya Gutkovskiy, Dec 26 2016

Examples

			a(1) = 2 because sigma_3(2) = 1^3 + 2^3 = 9 and 9 == 1 (mod 2);
a(2) = 3 because sigma_3(3) = 1^3 + 3^3 = 28 and 28 == 1 (mod 3);
a(3) = 4 because sigma_3(4) = 1^3 + 2^3 + 4^3 = 73 and 73 == 1 (mod 4), etc.
		

Crossrefs

Cf. A000040, A000430, A001158, A001248, A030078, A087797.

Programs

Mathematica

Select[Range[300], Mod[DivisorSigma[3, #1], #1] == 1 & ]

Extensions

Edited by Ilya Gutkovskiy, Dec 26 2016