E.g.f. 1/(1-4x-x^2).A052630E.g.f. 1/(1-4x-x^2).Terms a(0) =1a(1) =4a(2) =34a(3) =432a(4) =7320a(5) =155040a(6) =3940560a(7) =116847360a(8) =3959786880a(9) =150965337600External referencesoeis: A052630