a(n) = A007678(2*n)/(2*n).

Terms

a(0) =0a(1) =1a(2) =4a(3) =10a(4) =22a(5) =37a(6) =68a(7) =106a(8) =137a(9) =225a(10) =310a(11) =376a(12) =538a(13) =685a(14) =716a(15) =1058a(16) =1288a(17) =1471a(18) =1842a(19) =2170a(20) =2327a(21) =2941a(22) =3388a(23) =3734a(24) =4412a(25) =4993a(26) =5444a(27) =6306a(28) =7042a(29) =7391