A068406 Numbers n such that n and 2n+1 have the same number of prime divisors.

2, 3, 4, 5, 8, 9, 10, 11, 13, 22, 23, 28, 29, 34, 38, 41, 45, 46, 53, 55, 57, 58, 72, 76, 77, 80, 81, 83, 85, 87, 88, 89, 91, 92, 93, 94, 100, 104, 106, 108, 112, 113, 117, 118, 121, 122, 123, 124, 125, 128, 129, 131, 133, 143, 145, 147, 148, 152, 159, 160, 161, 162

Offset

1,1

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Formula

n such that omega(n)=omega(2n+1).

Mathematica

Select[Range[162], PrimeNu[#] == PrimeNu[2 # + 1] &] (* Ivan Neretin, Apr 30 2016 *)

Prog

(PARI) is(n)=omega(n)==omega(2*n+1) \\ Charles R Greathouse IV, Apr 30 2016

Crossrefs

Cf. A117360.

Sequence in context: A004827 A155941 A046892 * A276878 A047247 A169606

Adjacent sequences: A068403 A068404 A068405 * A068407 A068408 A068409

Keyword

easy,nonn

Author

Benoit Cloitre, Mar 09 2002

Status

approved