a(n) = 2*binomial(4*n + 8, n)/(n + 2).

Terms

a(0) =1a(1) =8a(2) =60a(3) =456a(4) =3542a(5) =28080a(6) =226548a(7) =1855040a(8) =15380937a(9) =128896456a(10) =1090119316a(11) =9292881360a(12) =79769043900a(13) =688915123680