A124342 Expansion of (1+x)/(1+2x-2x^3).

1, -1, 2, -2, 2, 0, -4, 12, -24, 40, -56, 64, -48, -16, 160, -416, 800, -1280, 1728, -1856, 1152, 1152, -6016, 14336, -26368, 40704, -52736, 52736, -24064, -57344, 220160, -488448, 862208, -1284096, 1591296, -1458176, 348160

Offset: 0

Author

Paul Barry, Oct 26 2006

Keywords

• easy
• sign

Comments

Diagonal sums of A124341. Binomial transform has g.f. (1-x)/(1-x-x^2-x^3).

Links

• Index entries for linear recurrences with constant coefficients, signature (-2,0,2).

Formula

a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, (-1)^(n-k-j)*C(n-k,j)*C(k,j-k)}}

a(n) = (-1)^(n+1)*A073358(n+1). - R. J. Mathar, Feb 04 2014

a(n) = A077988(n-1)+A077988(n). - R. J. Mathar, Jan 25 2016