If 0 <= n <= 3 then a(n) = n(n+1)(n+2)/3, if n >= 4 then a(n) = n(n^2+5)/3.

Terms

a(0) =0a(1) =2a(2) =8a(3) =20a(4) =28a(5) =50a(6) =82a(7) =126a(8) =184a(9) =258a(10) =350a(11) =462a(12) =596a(13) =754a(14) =938a(15) =1150a(16) =1392a(17) =1666a(18) =1974a(19) =2318a(20) =2700a(21) =3122a(22) =3586a(23) =4094a(24) =4648a(25) =5250a(26) =5902a(27) =6606a(28) =7364a(29) =8178