E.g.f. satisfies y'' + y' + x^3*y = 0 with y(0)=0, y'(0)=1.

Terms

a(0) =0a(1) =1a(2) =-1a(3) =1a(4) =-1a(5) =1a(6) =-25a(7) =85a(8) =-205a(9) =415a(10) =-751a(11) =13351a(12) =-74551a(13) =277501a(14) =-825301a(15) =2114017a(16) =-31272601a(17) =234796831a(18) =-1167200191a(19) =4534428271a(20) =-14884655503a(21) =196703557717