a(n) = n^4/8 if n is even, a(n) = (n^2-1)^2/8 if n is odd.

Terms

a(0) =0a(1) =0a(2) =2a(3) =8a(4) =32a(5) =72a(6) =162a(7) =288a(8) =512a(9) =800a(10) =1250a(11) =1800a(12) =2592a(13) =3528a(14) =4802a(15) =6272a(16) =8192a(17) =10368a(18) =13122a(19) =16200a(20) =20000a(21) =24200a(22) =29282a(23) =34848a(24) =41472a(25) =48672a(26) =57122a(27) =66248a(28) =76832a(29) =88200