a(n) = (7*n)!*(n/2)!/((7*n/2)!*(n)!*(3*n)!).

A364520

a(n) = (7*n)!*(n/2)!/((7*n/2)!*(n)!*(3*n)!).

Terms

    a(0) =1a(1) =64a(2) =12012a(3) =2621440a(4) =608435100a(5) =146028888064

External references