A112754 - OEIS

%I #7 Feb 06 2020 07:13:47

%S 0,1,1,2,2,2,3,3,3,4,3,4,4,5,4,5,4,5,6,5,6,5,6,7,5,6,7,6,7,8,6,7,8,6,

%T 7,8,9,7,8,9,7,8,9,10,7,8,9,10,8,9,10,11,8,9,10,11,8,9,10,11,12,9,10,

%U 11,12,9,10,11,12,13,9,10,11,12,13,10,11,12,13,14,10,11,12,13,14,10,11,12

%N Total number of prime factors of n-th number of the form 3^i*5^j.

%H Amiram Eldar, <a href="/A112754/b112754.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A001222(A003593(n)) = A022336(n) + A022337(n).

%t s = {}; m = 12; Do[n = 5^k; While[n <= 5^m, AppendTo[s, n]; n *= 3], {k, 0, m}]; PrimeOmega[Union[s]] (* _Amiram Eldar_, Feb 06 2020 *)

%Y Cf. A001222, A003593, A022336, A022337, A069352, A112753, A112759.

%K nonn

%O 1,4

%A _Reinhard Zumkeller_, Sep 18 2005