a(0)=1, a(n) = sigma_3(2n).

Terms

a(0) =1a(1) =9a(2) =73a(3) =252a(4) =585a(5) =1134a(6) =2044a(7) =3096a(8) =4681a(9) =6813a(10) =9198a(11) =11988a(12) =16380a(13) =19782a(14) =25112a(15) =31752a(16) =37449a(17) =44226a(18) =55261a(19) =61740a(20) =73710a(21) =86688a(22) =97236a(23) =109512a(24) =131068a(25) =141759a(26) =160454a(27) =183960a(28) =201240a(29) =219510