E.g.f. (1-2x^2)/(1-x-2x^2).

A052653

E.g.f. (1-2x^2)/(1-x-2x^2).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =18a(4) =120a(5) =1320a(6) =15120a(7) =216720a(8) =3427200a(9) =62052480a(10) =1237420800a(11) =27263174400a(12) =653837184000

External references