a(n) = 2^n * binomial(4*n,n).

Terms

a(0) =1a(1) =8a(2) =112a(3) =1760a(4) =29120a(5) =496128a(6) =8614144a(7) =151557120a(8) =2692684800a(9) =48201359360a(10) =868004380672