Empirical: a(n) = (1/2951082477025093078506985205425766400000000)*n^39 + (1/9265565077001862098923030472294400000000)*n^38 + (4759/286744856067215521798249574616268800000000)*n^37 + (101/54384989296769183840350796513280000000)*n^36 + (4297/26909239495797252421006904524800000000)*n^35 + (500161/46130124849938147007440407756800000000)*n^34 + (1043071/1625219875178695333385758310400000000)*n^33 + (125831/3888633058133401923653468160000000)*n^32 + (2881246861/2072155340852836550066841845760000000)*n^31 + (1053952379/18567700186853374104541593600000000)*n^30 + (2385513601853/1225468212332322690899745177600000000)*n^29 + (6461595793/123831573811526860265226240000000)*n^28 + (405970748744083/183115939773795344617203302400000000)*n^27 + (49033699601/1916441023273629980295168000000)*n^26 + (18461254552442269/33806019650546832852406763520000000)*n^25 + (10587289948256711/118617612808936255622479872000000)*n^24 - (1289806696565094391/395800505550479447996497920000000)*n^23 + (201884626837893793/2458388233232791602462720000000)*n^22 + (126964526201660079053791/43159463822634889372835512320000000)*n^21 - (120694982083307696310661/352322153654162362227228672000000)*n^20 + (1675653569377629658124395343/93701467509667851927866572800000000)*n^19 - (263287040670773979099643859/410971348726613385648537600000000)*n^18 + (1973491406041293829953804008773/112686732168489442841355878400000000)*n^17 - (40851247913095487402611463069/106141348981308737370193920000000)*n^16 + (1019606489016701846854504725921653/137336954830346508462902476800000000)*n^15 - (64228797335699946609244269895781/431199230236566745566412800000000)*n^14 + (10170112301125459687679918106593153/2881194856580695981739212800000000)*n^13 - (1890238239930047371468073141513273/21342184122819970235105280000000)*n^12 + (1381046763043372748429138266139542127/696288757007001528920309760000000)*n^11 - (6048100811967496545717727374532578677/165783037382619411647692800000000)*n^10 + (70600338335550729825999489198886211730509/131908036744104178534347571200000000)*n^9 - (368495379582593251065062404421360959963/59822238886215046954352640000000)*n^8 + (282040404445916695314702915578197619075851/5190825520022618136768307200000000)*n^7 - (3193980141012310595608437405903551031149/9106711438636172169768960000000)*n^6 + (6395779800010992038938555013521670219129/4325687933352181780640256000000)*n^5 - (52994428840760816207125885706156003/21855187234316947230720000)*n^4 - (268757139031074527373440415982821419843/20373357051590182072392960000)*n^3 + (13722257905966761829311389014925857/138199410199363601088000)*n^2 - (1413449376368458398199264453/5342931457063200)*n + 252835817594 for n>22