A068406 - OEIS

%I #10 Apr 30 2016 19:47:09

%S 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,

%T 80,81,83,85,87,88,89,91,92,93,94,100,104,106,108,112,113,117,118,121,

%U 122,123,124,125,128,129,131,133,143,145,147,148,152,159,160,161,162

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

%H Ivan Neretin, <a href="/A068406/b068406.txt">Table of n, a(n) for n = 1..10000</a>

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

%t Select[Range[162], PrimeNu[#] == PrimeNu[2 # + 1] &] (* _Ivan Neretin_, Apr 30 2016 *)

%o (PARI) is(n)=omega(n)==omega(2*n+1) \\ _Charles R Greathouse IV_, Apr 30 2016

%Y Cf. A117360.

%K easy,nonn

%O 1,1

%A _Benoit Cloitre_, Mar 09 2002