a(n) = (4/3)*u*(u^3+6*u^2+8*u-3) where u=floor((3*n+5)/2).

Terms

a(0) =1008a(1) =2080a(2) =6440a(3) =10208a(4) =22360a(5) =31416a(6) =57408a(7) =75208a(8) =122816a(9) =153680a(10) =232408a(11) =281520a(12) =402600a(13) =476008a(14) =652400a(15) =757016a(16) =1003408a(17) =1147008a(18) =1479816a(19) =1671040a(20) =2108408a(21) =2356760a(22) =2918560a(23) =3234408a(24) =3942240a(25) =4336816a(26) =5214008a(27) =5699408a(28) =6771016a(29) =7360200