a(n) = n^2*(n^3+1)/2.

Terms

a(0) =0a(1) =1a(2) =18a(3) =126a(4) =520a(5) =1575a(6) =3906a(7) =8428a(8) =16416a(9) =29565a(10) =50050a(11) =80586a(12) =124488a(13) =185731a(14) =269010a(15) =379800a(16) =524416a(17) =710073a(18) =944946a(19) =1238230a(20) =1600200a(21) =2042271a(22) =2577058a(23) =3218436a(24) =3981600a(25) =4883125a(26) =5941026a(27) =7174818a(28) =8605576a(29) =10255995