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

A052585

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

Terms

    a(0) =1a(1) =1a(2) =6a(3) =30a(4) =264a(5) =2520a(6) =30960a(7) =428400a(8) =6894720a(9) =123742080a(10) =2478470400a(11) =54486432000

External references