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 A115378 a(n) = number of positive integers k < n such that n XOR k = (n+k). 1

%I

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

%C The number of positive integers k < n such that n XOR k = (n-k) is A038573(n).

%F a(n) = -1 + 2^(number of 0's in binary expansion of n). a(n) = 2^A080791(n) - 1 = A080100(n) - 1.

%o (PARI) a(n)=sum(k=1,n,if(bitxor(n,k)==(n+k),1,0))

%Y Cf. A080791, A080100, A038573.

%K nonn

%O 1,4

%A _Paul D. Hanna_, Jan 21 2006

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Last modified February 21 04:18 EST 2019. Contains 320371 sequences. (Running on oeis4.)