%I #9 Apr 10 2023 10:51:45
%S -1,-1,1,5,9,11,17,59,237,849,2861,9625,33057,115753,410581,1469325,
%T 5296449,19216691,70134489,257320475,948545125,3511308899,13047504065,
%U 48649662439,181967395749,682578873479,2567177040641,9678602093387,36571567691029
%N Expansion of -1/(1 - x * sqrt(1-4*x)).
%F a(n) = -Sum_{k=0..n} (-4)^k * binomial((n-k)/2,k).
%o (PARI) my(N=30, x='x+O('x^N)); Vec(-1/(1-x*sqrt(1-4*x)))
%Y Cf. A000984, A362157.
%K sign,easy
%O 0,4
%A _Seiichi Manyama_, Apr 09 2023