a(n) = (2*n+2)!/((n+2)*n!).

A092956

a(n) = (2*n+2)!/((n+2)*n!).

Terms

    a(0) =1a(1) =8a(2) =90a(3) =1344a(4) =25200a(5) =570240a(6) =15135120a(7) =461260800a(8) =15878903040a(9) =609493248000

External references