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

Terms

a(0) =0a(1) =1a(2) =14a(3) =99a(4) =424a(5) =1325a(6) =3366a(7) =7399a(8) =14624a(9) =26649a(10) =45550a(11) =73931a(12) =114984a(13) =172549a(14) =251174a(15) =356175a(16) =493696a(17) =670769a(18) =895374a(19) =1176499a(20) =1524200a(21) =1949661a(22) =2465254a(23) =3084599a(24) =3822624a(25) =4695625a(26) =5721326a(27) =6918939a(28) =8309224a(29) =9914549