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%I #21 Jul 11 2020 10:09:52
%S 9,15,21,35,51,93,119,155,381,527,635,771,1799,2159,7967,24573,32639,
%T 40955,139247,196611,393213,458759,655355,1572861,2031647,2105087,
%U 2228207,2621435,8323199,8912879,33685247,134741759,536813567,6442450941,8590000127,10737418235
%N Semiprimes that are product of a Fermat prime and a Mersenne prime.
%C As 3 is both a Fermat prime and a Mersenne prime, A019434(1) * A000668(1) = 9 is also a term. It is the only square in this sequence.
%F A335885(a(n)) = 2.
%o (PARI)
%o isA000668(n) = (isprime(n)&&!bitand(n,1+n));
%o isA019434(n) = ((n>2)&&isprime(n)&&!bitand(n-2,n-1));
%o isA336115(n) = if(9==n,1, if((2!=omega(n))||(2!=bigomega(n)),0,my(ps=factor(n)[,1]); (isA019434(ps[1])&&isA000668(ps[2]))||(isA019434(ps[2])&&isA000668(ps[1])))); \\ _Antti Karttunen_, Jul 11 2020
%Y Cf. A000265, A000668, A019434, A144482, A333788, A335885.
%Y Subsequence of A335912.
%K nonn
%O 1,1
%A _Antti Karttunen_, Jul 09 2020
%E Missing terms and more terms added by _Jinyuan Wang_, Jul 11 2020
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