Empirical: a(n) = (1/1656632731900575744000000)*n^28 - (1/23666181884293939200000)*n^27 + (11309/3760293343837814784000000)*n^26 - (204751/1880146671918907392000000)*n^25 + (5237983/1306207161543661977600000)*n^24 - (1279703/15041173375351259136000)*n^23 + (861471343/397541310035027558400000)*n^22 - (1201515899/49047304484841062400000)*n^21 + (3209215813/5162874156299059200000)*n^20 - (1669654907/3269820298989404160000)*n^19 + (810515799997/5162874156299059200000)*n^18 + (59691410423/66190694311526400000)*n^17 + (40834059095189/708629786158694400000)*n^16 - (38551806224791/30369847978229760000)*n^15 + (240445960224280579/3340683277605273600000)*n^14 - (77791071093959777/50616413297049600000)*n^13 + (406584181341859508861/14197903929822412800000)*n^12 - (1349153478409709863/3911268300226560000)*n^11 + (450700327126672543660339/128749174272707788800000)*n^10 - (234686822864201848263293/9196369590907699200000)*n^9 + (1209198062617246926059711/7663641325756416000000)*n^8 - (66446367649732205186663/85151570286182400000)*n^7 + (144651793670107177939883/42949256942592000000)*n^6 - (81467721712145040823501/5230999243008000000)*n^5 + (13626253162677461685571/183727376921088000)*n^4 - (1860146455809918292669/5666915846592000)*n^3 + (271452150679824971/139491752400)*n^2 - (67945121462968483/6692786100)*n + 22313118 for n>8