a(n) = (n-1)!(n+2)!/(3*2^n).

A067550

a(n) = (n-1)!(n+2)!/(3*2^n).

Terms

    a(0) =1a(1) =2a(2) =10a(3) =90a(4) =1260a(5) =25200a(6) =680400a(7) =23814000a(8) =1047816000a(9) =56582064000

External references