a(n) = A027144(2n, n).

Terms

a(0) =1a(1) =4a(2) =12a(3) =80a(4) =304a(5) =2176a(6) =8832a(7) =64768a(8) =271104a(9) =2013184a(10) =8579072a(11) =64200704a(12) =276815872a(13) =2082406400a(14) =9053405184a(15) =68364861440a(16) =299056168960