a(n) = (5*n)!/((n!)^2*(3*n + 1)!).

A383439

a(n) = (5*n)!/((n!)^2*(3*n + 1)!).

Terms

    a(0) =1a(1) =5a(2) =180a(3) =10010a(4) =678300a(5) =51482970a(6) =4206302100a(7) =361913666400

External references