A340370 - OEIS

%I #7 Jan 07 2021 08:37:13

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

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

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

%N a(n) = 1 if the odd part of n is a squarefree semiprime, 0 otherwise.

%H Antti Karttunen, <a href="/A340370/b340370.txt">Table of n, a(n) for n = 1..65537</a>

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

%F a(n) = A280710(A000265(n)).

%o (PARI)

%o A000265(n) = (n>>valuation(n,2));

%o A280710(n) = (bigomega(n)==2*issquarefree(n)); \\ After code in A280710.

%o A340370(n) = A280710(A000265(n));

%Y Characteristic function of A340380.

%Y Cf. A000265, A280710.

%Y Cf. also A340371.

%K nonn

%O 1

%A _Antti Karttunen_, Jan 06 2021