%I #6 Feb 05 2024 18:07:29

%S 0,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,1,0,0,1,0,0,0,

%T 1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,

%U 0,0,1,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,1,0,0,1

%N a(n) = 1 if n' is odd and also n'' is odd, otherwise 0, where n' stands for the arithmetic derivative, A003415.

%H Antti Karttunen, <a href="/A369655/b369655.txt">Table of n, a(n) for n = 0..100000</a>

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>

%F a(n) = A165560(n) * A165560(A003415(n)).

%o (PARI)

%o A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));

%o A369655(n) = { my(u=A003415(n)); ((u%2) && (A003415(u)%2)); };

%Y Characteristic function of A369656.

%Y Cf. A000035, A003415, A068346, A165560.

%K nonn

%O 0

%A _Antti Karttunen_, Feb 05 2024