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

1,2

Comments

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

Links

Table of n, a(n) for n=1..84.

Formula

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

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 *)

Crossrefs

Cf. A001222, A062173.

Sequence in context: A281995 A304452 A292763 * A381241 A157201 A067351

Adjacent sequences: A176172 A176173 A176174 * A176176 A176177 A176178

Keyword

nonn

Author

Juri-Stepan Gerasimov, Dec 07 2010

Status

approved