Empirical: a(n) = (114400861/793412278431252480000)*n^24 + (9239627879/957482101440184320000)*n^23 + (44310950533/79341227843125248000)*n^22 + (2127240652507/102181884343418880000)*n^21 + (104806039047067/175168944588718080000)*n^20 + (8655398246669/663518729502720000)*n^19 + (45578431273829/201674771730432000)*n^18 + (2769092925285143/896332318801920000)*n^17 + (127801713591820043/3796230997278720000)*n^16 + (91667397382733927/316352583106560000)*n^15 + (1152509683968623173/596550585286656000)*n^14 + (4880801325983561777/497125487738880000)*n^13 + (1496893008354410269843/41758540970065920000)*n^12 + (1156023598739370173/13181357629440000)*n^11 + (25564058819990612809/189811549863936000)*n^10 + (434837239525294013/3594915717120000)*n^9 + (13576368314077746449/33894919618560000)*n^8 - (6484820348810144197/12004450698240000)*n^7 - (8140450104179952211/5008915899187200)*n^6 - (7546772065962622733249/88699552381440000)*n^5 + (45447028575164331235163/162615846032640000)*n^4 - (1224189669612415214921/1355132050272000)*n^3 + (2291702927114699767/1075501627200)*n^2 - (7775783786220287/2677114440)*n + 1579223 for n>3