login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A077905
Expansion of 1/(1 - x^2 - x^3 + x^4).
2
1, 0, 1, 1, 0, 2, 0, 1, 2, -1, 3, 0, 0, 4, -3, 4, 1, -3, 8, -6, 4, 5, -10, 15, -9, 0, 16, -24, 25, -8, -15, 41, -48, 34, 8, -55, 90, -81, 27, 64, -144, 172, -107, -36, 209, -315, 280, -70, -244, 525, -594, 351, 175, -768, 1120, -944, 177, 944, -1887, 2065, -1120, -766, 2832, -3951, 3186, -353, -3597, 6784, -7136
OFFSET
0,6
FORMULA
a(n) = sum(k=1..n/2, sum(j=0..k, binomial(j,n-4*k+2*j)*(-1)^(k-j)*binomial(k,j))), n>0, a(0)=1. - Vladimir Kruchinin, Oct 21 2011
a(-3-n) = -A023434(n) for all n in Z. - Michael Somos, Sep 25 2014
EXAMPLE
G.f. = 1 + x^2 + x^3 + 2*x^5 + x^7 + 2*x^8 - x^9 + 3*x^10 + 4*x^13 + ...
MATHEMATICA
CoefficientList[ Series[1/((1 - x) (1 + x - x^3)), {x, 0, 68}], x] (* Robert G. Wilson v, Oct 29 2011 *)
CROSSREFS
Cf. A023434.
Sequence in context: A029389 A025835 A029277 * A131331 A268696 A020513
KEYWORD
sign,easy
AUTHOR
N. J. A. Sloane, Nov 17 2002
STATUS
approved