A244986 - OEIS

A244986

a(n) = Position of 2^n among the numbers which are divisible by the square of their highest noncomposite factor (i.e., the union of {1} and A070003), 0 if not there.

%I #10 Jul 16 2017 14:47:40

%S 1,0,2,3,5,9,14,23,37,58,90,143,225,355,563,894,1426,2277,3643,5839,

%T 9398,15155,24518,39758,64607,105250,171874,281237,461255,758040,

%U 1248270

%N a(n) = Position of 2^n among the numbers which are divisible by the square of their highest noncomposite factor (i.e., the union of {1} and A070003), 0 if not there.

%F For all n >= 1, a(n+1) = A244984(A006254(n)).

%e 2 is not divisible by 2^2, thus a(2) = 0, the only zero in the sequence.

%e 2^4 = 16 is the fifth term in [1, 4, 8, 9, 16, 18, 25, 27, 32, 36, ...] (the union of {1} and A070003), thus a(4) = 5.

%e 2^5 = 32 is the ninth term in the same list, thus a(5) = 9.

%Y From a(2) onward one more than A244985.

%Y Cf. A000079, A070003, A006254, A244984.

%K nonn

%O 0,3

%A _Antti Karttunen_, Jul 21 2014