A068406 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

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