%I #9 Apr 22 2022 10:41:02
%S 0,0,0,1,0,1,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,1,
%T 0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,
%U 0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,1
%N a(n) = 1 if n is an even semiprime (2*prime), otherwise 0.
%H Antti Karttunen, <a href="/A353478/b353478.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 If A000035(n) = 0, then a(n) = A010051(n/2), otherwise 0.
%F a(n) = A059841(n) * A064911(n).
%F a(n) = A064911(n) - A353480(n).
%o (PARI) A353478(n) = ((0==(n%2)) && isprime(n/2));
%Y Characteristic function of A100484, the primes doubled.
%Y Cf. A000035, A010051, A059841, A064911, A353477, A353479, A353480.
%K nonn
%O 1
%A _Antti Karttunen_, Apr 22 2022