a(n) = (36*n^6 - 60*n^5 + 30*n^4 + 4*n^3 + 8*n^2 - 4*n + 1 - (-1)^n)/8.

Terms

a(0) =0a(1) =2a(2) =115a(3) =1783a(4) =11758a(5) =49304a(6) =156633a(7) =412589a(8) =949564a(9) =1973662a(10) =3788095a(11) =6819827a(12) =11649450a(13) =19044308a(14) =29994853a(15) =45754249a(16) =67881208a(17) =98286074a(18) =139280139a(19) =193628207a(20) =264604390a(21) =356051152a(22) =472441585a(23) =618944933a(24) =801495348a(25) =1026863894a(26) =1302733783a(27) =1637778859a(28) =2041745314a(29) =2525536652