a(n) = n * binomial(4*n, n).

Terms

a(0) =0a(1) =4a(2) =56a(3) =660a(4) =7280a(5) =77520a(6) =807576a(7) =8288280a(8) =84146400a(9) =847289520a(10) =8476605280a(11) =84362730452a(12) =836022413616