A151758 G.f.: Theta^2-Theta, where Theta = Sum_{k>=0} x^(2^k).

0, -1, 0, 2, 0, 2, 2, 0, 0, 2, 2, 0, 2, 0, 0, 0, 0, 2, 2, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0

Offset: 0

Author

N. J. A. Sloane, Jun 22 2009

Keywords

• sign

Comments

If we omit the "-x" term and divide by 2, we get the characteristic function of the numbers with binary weight 2 (A018900, A151774).

Crossrefs

Cf. A000079, A073267, A151759, A151760, A151761, A151762, A018900, A151774.

Programs

Mathematica

w[n_] := IntegerDigits[n, 2] // Total;
a[n_] := If[n == 1, -1, 2 Boole[w[n] == 2]];
a /@ Range[0, 104] (* Jean-François Alcover, Mar 31 2021 *)