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”).
%I #7 Jan 25 2016 12:36:23
%S 1,-1,2,-2,2,0,-4,12,-24,40,-56,64,-48,-16,160,-416,800,-1280,1728,
%T -1856,1152,1152,-6016,14336,-26368,40704,-52736,52736,-24064,-57344,
%U 220160,-488448,862208,-1284096,1591296,-1458176,348160
%N Expansion of (1+x)/(1+2x-2x^3).
%C Diagonal sums of A124341. Binomial transform has g.f. (1-x)/(1-x-x^2-x^3).
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-2,0,2).
%F 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)}}
%F a(n) = (-1)^(n+1)*A073358(n+1). - _R. J. Mathar_, Feb 04 2014
%F a(n) = A077988(n-1)+A077988(n). - _R. J. Mathar_, Jan 25 2016
%K easy,sign
%O 0,3
%A _Paul Barry_, Oct 26 2006