A372468 - OEIS

%I #7 May 02 2024 10:06:35

%S 1,2,2,2,4,2,4,4,2,2,4,4,2,2,4,4,2,8,4,4,2,8,2,4,4,4,2,4,4,8,2,8,2,4,

%T 2,4,2,8,4,8,4,4,2,2,4,4,8,2,4,8,2,2,4,4,8,2,4,2,4,4,4,8,2,4,4,4,4,2,

%U 2,8,2,8,8,4,2,2,8,4,2,8,4,4,4,16,4,4,4

%N The number of divisors of the numbers whose number of divisors is a power of 2 (A036537).

%C Also, the number of infinitary divisors of the numbers whose number of divisors is a power of 2.

%H Amiram Eldar, <a href="/A372468/b372468.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A000005(A036537(n)).

%F a(n) = A037445(A036537(n)).

%F a(n) = A372470(A036537(n)).

%F a(n) = 2^A372469(n).

%t Select[DivisorSigma[0, Range[300]], # == 2^IntegerExponent[#, 2] &]

%o (PARI) lista(n) = select(x -> x >> valuation(x, 2) == 1, vector(n, i, numdiv(i)));

%Y Cf. A000005, A036537, A037445, A372469, A372470.

%K nonn,easy

%O 1,2

%A _Amiram Eldar_, May 02 2024