A354711 Numbers k such that the number of divisors of k divides k-1.

1, 3, 4, 5, 7, 11, 13, 16, 17, 19, 21, 23, 25, 29, 31, 33, 37, 41, 43, 47, 49, 53, 57, 59, 61, 64, 65, 67, 69, 71, 73, 77, 79, 81, 83, 85, 89, 93, 97, 100, 101, 103, 105, 107, 109, 113, 121, 125, 127, 129, 131, 133, 137, 139, 141, 145, 149, 151, 157, 161, 163, 167, 169, 173, 175, 177, 179, 181

Offset: 1

Author

Max Alekseyev, Jun 03 2022

Keywords

• nonn

Comments

Numbers k such that k == 1 (mod A000005(k)).

Every odd prime is a term. Nonprime terms are listed in A354712.

Crossrefs

Cf. A000005, A033950, A272872, A354712, A354714, A354715, A354716.

Programs

Mathematica

Select[Range[200], Divisible[# - 1, DivisorSigma[0, #]] &] (* Amiram Eldar, Jun 03 2022 *)