Empirical: a(n) = (1/20397882081197443358640281739902897356800000000)*n^39 + (1/750750168612346093435417068086231040000000)*n^37 + (1/185996663394950608733999724075417600000000)*n^36 + (8837/743986653579802434935998896301670400000000)*n^35 + (631/1771396794237624845085711657861120000000)*n^34 + (176177/6564588119821786190611754967367680000000)*n^33 + (14929/2960221915504052214381202636800000000)*n^32 - (50345303/351047493038598192011323795046400000000)*n^31 + (3012151/123403792011087040202491822080000000)*n^30 - (3368071747/7842996558926865221758369136640000000)*n^29 + (17783471/1254397760688194168920473600000000)*n^28 + (374581523821/137635643292352481730546892800000000)*n^27 - (745569243611/3863545102919638040275058688000000)*n^26 + (1393908686578201/121701670741968598268664348672000000)*n^25 - (69410878550330237/202836117903280997114440581120000000)*n^24 + (33405814918334622997/11034284813938486243025567612928000000)*n^23 + (189087219484973/401866559488208658235392000000)*n^22 - (4921452845127022244977/149159106971026177672519530577920000)*n^21 + (3344690464067036312797/2596057974293827932200632320000000)*n^20 - (3194553488408276960898246737/107944090571137365420902291865600000000)*n^19 + (395502342632549869795213/2516179267392479380440612864000000)*n^18 + (4197804081886045761812607949/221275764985397451397571543040000000)*n^17 - (5814402579732912796391505541/6299258319977670717839769600000000)*n^16 + (83619019420279453063992995005321/3489974381571158332704345292800000000)*n^15 - (1310575957400732133915995868031/3622073533987160662757867520000000)*n^14 + (251121781100445624770442293233301/228190632641191121753745653760000000)*n^13 + (870835749250548675887138257281673/8643584569742087945217638400000000)*n^12 - (505120269757166152678427859552251717/167109301681680366940874342400000000)*n^11 + (659564134922563902188665284719009/13719975507527123722567680000000)*n^10 - (825557371041894917929170030461524471/1851340866583918295218913280000000)*n^9 + (22377682398297895696927234375882703/18420337486957712405299200000000)*n^8 + (260967926357485602000453891218692132093/8494078123673375132893593600000000)*n^7 - (753778831121625659224348429374433207/1409273896838719856136192000000)*n^6 + (233676164984020660778517254506589908727/51908255200226181367683072000000)*n^5 - (5709847452312637732393335894742873/260191755389604919136256000)*n^4 + (5759677080325173937944291257513981531/112053463783746001398161280000)*n^3 + (99969630582155955292900441/2924408242818316800)*n^2 - (2616936139067570428892297/5342931457063200)*n + 821211181 for n>14