a(n) = (2*n^3 + 5*n^2 - 17*n)/2.

Terms

a(0) =-5a(1) =1a(2) =24a(3) =70a(4) =145a(5) =255a(6) =406a(7) =604a(8) =855a(9) =1165a(10) =1540a(11) =1986a(12) =2509a(13) =3115a(14) =3810a(15) =4600a(16) =5491a(17) =6489a(18) =7600a(19) =8830a(20) =10185a(21) =11671a(22) =13294a(23) =15060a(24) =16975a(25) =19045a(26) =21276a(27) =23674a(28) =26245a(29) =28995