G.f. satisfies A(x) = 1 + x / (1 + x*A(x))^4.

Terms

a(0) =1a(1) =1a(2) =-4a(3) =6a(4) =16a(5) =-119a(6) =240a(7) =630a(8) =-5656a(9) =13044a(10) =31568a(11) =-323102a(12) =816172a(13) =1772553a(14) =-20373748a(15) =55339784a(16) =105991968a(17) =-1366239119a(18) =3950894080a(19) =6570520544a(20) =-95534073488a(21) =292319792622a(22) =414994066768