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

Terms

a(0) =1a(1) =1a(2) =4a(3) =6a(4) =12a(5) =20a(6) =80a(7) =152a(8) =304a(9) =528a(10) =2176a(11) =4416a(12) =8832a(13) =15488a(14) =64768a(15) =135552a(16) =271104a(17) =477440a(18) =2013184a(19) =4289536a(20) =8579072a(21) =15144960a(22) =64200704a(23) =138407936a(24) =276815872a(25) =489431040a(26) =2082406400a(27) =4526702592a(28) =9053405184a(29) =16024403968