G.f.: 1/(1+2*x-9*x^2-10*x^3+5*x^4).

Terms

a(0) =1a(1) =-2a(2) =13a(3) =-34a(4) =160a(5) =-486a(6) =2007a(7) =-6618a(8) =25639a(9) =-88340a(10) =331216a(11) =-1168012a(12) =4305373a(13) =-15368994a(14) =56150145a(15) =-201727446a(16) =733589392a(17) =-2644379378a(18) =9593038099a(19) =-34640959450a(20) =125507521051a(21) =-453631399272