a(n) = n^8*(n + 1)/2.

Terms

a(0) =0a(1) =1a(2) =384a(3) =13122a(4) =163840a(5) =1171875a(6) =5878656a(7) =23059204a(8) =75497472a(9) =215233605a(10) =550000000a(11) =1286153286a(12) =2794881024a(13) =5710115047a(14) =11068417920a(15) =20503125000a(16) =36507222016a(17) =62781816969a(18) =104689625472a(19) =169835630410a(20) =268800000000a(21) =416051452971a(22) =631072545664