a(n) = n^5 - n^3.

Terms

a(0) =0a(1) =0a(2) =24a(3) =216a(4) =960a(5) =3000a(6) =7560a(7) =16464a(8) =32256a(9) =58320a(10) =99000a(11) =159720a(12) =247104a(13) =369096a(14) =535080a(15) =756000a(16) =1044480a(17) =1414944a(18) =1883736a(19) =2469240a(20) =3192000a(21) =4074840a(22) =5142984a(23) =6424176a(24) =7948800a(25) =9750000a(26) =11863800a(27) =14329224a(28) =17188416a(29) =20486760