A176175 Numbers k such that (2^(k-1) mod k) = number of prime divisors of k (counted with multiplicity).

1, 3, 5, 6, 7, 10, 11, 13, 14, 17, 19, 22, 23, 26, 29, 31, 34, 37, 38, 41, 43, 46, 47, 53, 58, 59, 61, 62, 67, 71, 73, 74, 79, 82, 83, 86, 89, 94, 97, 101, 103, 106, 107, 109, 113, 118, 122, 127, 131, 134, 137, 139, 142, 146, 149, 151, 157, 158, 163, 166, 167, 173, 178, 179, 181, 191, 193, 194, 197, 199, 202, 206, 211, 214, 218, 223, 226, 227, 229, 233, 239, 241, 251, 254

Offset: 1

Author

Juri-Stepan Gerasimov, Dec 07 2010

Keywords

• nonn

Comments

How is this related to A085118? - R. J. Mathar, Jul 02 2025

Crossrefs

Cf. A001222, A062173.

Programs

Maple

for n from 1 to 180 do modp(2^(n-1),n) ;  if % = numtheory[bigomega](n) then printf("%d,",n) ; end if; end do: # R. J. Mathar, Dec 07 2010

Mathematica

Select[Range[254], PrimeOmega[#] == PowerMod[2, # - 1, #] &] (* Michael De Vlieger, Jul 02 2025 *)

Formula

{k: A001222(k) = A062173(k)}.