a(n) = n^7 - n.

Terms

a(0) =0a(1) =0a(2) =126a(3) =2184a(4) =16380a(5) =78120a(6) =279930a(7) =823536a(8) =2097144a(9) =4782960a(10) =9999990a(11) =19487160a(12) =35831796a(13) =62748504a(14) =105413490a(15) =170859360a(16) =268435440a(17) =410338656a(18) =612220014a(19) =893871720a(20) =1279999980a(21) =1801088520a(22) =2494357866a(23) =3404825424a(24) =4586471400a(25) =6103515600a(26) =8031810150