login
Number of divisors of 3-smooth numbers.
2

%I #11 Apr 15 2024 03:30:04

%S 1,2,2,3,4,4,3,6,5,6,8,4,6,9,10,8,7,12,5,12,12,8,15,10,14,16,6,9,18,

%T 15,16,20,12,10,21,20,7,18,24,18,11,24,25,14,20,28,24,12,8,27,30,21,

%U 22,32,30,13,16,30,35,28,24,9,36,36,14,24,33,40,35,26,18,40,42,15,32

%N Number of divisors of 3-smooth numbers.

%H Reinhard Zumkeller, <a href="/A086416/b086416.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A000005(A003586(n)).

%F a(n) = if A086414(n) = A086415(n) then A086414(n)+1 else (A086414(n)+1)*(A086415(n)+1).

%F a(n) = (A022328(n)+1)*(A022329(n)+1).

%t DivisorSigma[0, Select[Range[10000], # == 2^IntegerExponent[#, 2] * 3^IntegerExponent[#, 3] &]] (* _Amiram Eldar_, Apr 15 2024 *)

%Y Cf. A086414, A086415, A086417.

%Y Cf. A000005, A003586, A022328, A022329.

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Jul 18 2003