cp's OEIS Frontend

A115378 a(n) = number of positive integers k < n such that n XOR k = (n+k).

%I A115378 #3 Mar 30 2012 18:36:55
%S A115378 0,1,0,3,1,1,0,7,3,3,1,3,1,1,0,15,7,7,3,7,3,3,1,7,3,3,1,3,1,1,0,31,15,
%T A115378 15,7,15,7,7,3,15,7,7,3,7,3,3,1,15,7,7,3,7,3,3,1,7,3,3,1,3,1,1,0,63,
%U A115378 31,31,15,31,15,15,7,31,15,15,7,15,7,7,3,31,15,15,7,15,7,7,3,15,7,7,3,7,3
%N A115378 a(n) = number of positive integers k < n such that n XOR k = (n+k).
%C A115378 The number of positive integers k < n such that n XOR k = (n-k) is A038573(n).
%F A115378 a(n) = -1 + 2^(number of 0's in binary expansion of n). a(n) = 2^A080791(n) - 1 = A080100(n) - 1.
%o A115378 (PARI) a(n)=sum(k=1,n,if(bitxor(n,k)==(n+k),1,0))
%Y A115378 Cf. A080791, A080100, A038573.
%K A115378 nonn
%O A115378 1,4
%A A115378 _Paul D. Hanna_, Jan 21 2006