Empirical: a(n) = (1/20397882081197443358640281739902897356800000000)*n^39 + (1/523022617466601111760007224100074291200000000)*n^38 + (107/82582518547358070277895877489485414400000000)*n^37 + (1/16533036746217831887466642140037120000000)*n^36 + (4051/371993326789901217467999448150835200000000)*n^35 + (499/553561498199257764089284893081600000000)*n^34 + (870931/32822940599108930953058774836838400000000)*n^33 + (120893/18084264792897482618765165199360000000)*n^32 - (26662381/5967807381656169264192504515788800000000)*n^31 + (16720337/929999591967612476888344166400000000)*n^30 + (51699607637/78429965589268652217583691366400000000)*n^29 - (2032883/68563355863702538425466880000000)*n^28 + (194646289368863/39553042991139794437315913318400000000)*n^27 - (148564216229939/811344471613123988457762324480000000)*n^26 + (15757915713871523/2434033414839371965373286973440000000)*n^25 + (19401324807797/167460159259674713819971584000000)*n^24 - (208499379570230572199/11034284813938486243025567612928000000)*n^23 + (12292099924756893379/10384231897175311728802529280000000)*n^22 - (1547657103622295303334601/37289776742756544418129882644480000000)*n^21 + (381010628116870139974541/497197023236753925575065101926400000)*n^20 + (650877361574033375256023519/53972045285568682710451145932800000000)*n^19 - (491329851410902510750527977/333160773367707917965747814400000000)*n^18 + (90588477410784197325792196583/1521270884274607478358304358400000000)*n^17 - (10345708022734327595674284917/7244147067974321325515735040000000)*n^16 + (499971758358780489778604822852311/29664782243354845827986934988800000000)*n^15 + (78968241161311148647814982611381/380317721068651869589576089600000000)*n^14 - (8779037520531500721668364048667921/570476581602977804384364134400000000)*n^13 + (456264671985237216923281403153779/1152477942632278392695685120000000)*n^12 - (507457435340702390121827506273932001/83554650840840183470437171200000000)*n^11 + (3557563571068753251306600562216861/73681349947830849621196800000000)*n^10 + (4302786983579154845649383293084303229/21984672790684029755724595200000000)*n^9 - (4949497557936575389818309191340593/416494700969669977374720000000)*n^8 + (4263022884963231107700866879915021281787/23358714840101781615457382400000000)*n^7 - (19323591765148432745200937763284627/11878319267786311525785600000)*n^6 + (54390440182599635666497675642142721937/6488531900028272670960384000000)*n^5 - (17772201486960117673835217599084537/1373234264556248184330240000)*n^4 - (3836445914614903944199173858933010291/28013365945936500349540320000)*n^3 + (43283060824952519276393918097299/41459823059809080326400)*n^2 - (4103053774081508820211949/1335732864265800)*n + 3399776394 for n>15