%I #11 Jan 30 2020 21:29:17

%S 0,0,1,3,10,30,88,252,712,1992,5537,15323,42286,116506,320773,883191,

%T 2433112,6709832,18529067,51251265,142021430,394336930,1097215414,

%U 3059549286,8550284176,23947824960,67221675367,189102714045,533104654538

%N G.f.: (1-x)*(1-2*x-x^2-(1-x)*sqrt(1-2*x-3*x^2))/(2*x*(1-2*x-x^2)).

%F D-finite with recurrence: +(n+1)*a(n) +(-5*n+1)*a(n-1) +4*(n-2)*a(n-2) +8*(n-2)*a(n-3) +(-5*n+31)*a(n-4) +3*(-n+5)*a(n-5)=0. - _R. J. Mathar_, Jun 12 2015

%p (1-x)*(1-2*x-x^2-(1-x)*sqrt(1-2*x-3*x^2))/(2*x*(1-2*x-x^2)) ;

%p taylor(%,x=0,40) ;

%p gfun[seriestolist](%) ; # _R. J. Mathar_, Jun 12 2015

%K nonn

%O 1,4

%A _N. J. A. Sloane_, Jun 04 2015