Empirical: a(n) = (1/38778025108327464960000)*n^24 - (1/1077167364120207360000)*n^23 + (271/481714597618974720000)*n^22 - (271/4865804016353280000)*n^21 + (329/47037847633920000)*n^20 - (3011573/4865804016353280000)*n^19 + (201847337/4033495434608640000)*n^18 - (3131163979/896332318801920000)*n^17 + (7367505577/33894919618560000)*n^16 - (90625603843/7532204359680000)*n^15 + (886328672397677/1491376463216640000)*n^14 - (4336011874342787/165708495912960000)*n^13 + (10700610334299900941/10439635242516480000)*n^12 - (3754899897685498957/105450861035520000)*n^11 + (10575227853643845113/9684262748160000)*n^10 - (7902173942390163127/269007298560000)*n^9 + (49500427611829698411403/72026704189440000)*n^8 - (221315089805860513533347/16005934264320000)*n^7 + (250898398462572582113381239/1064394628577280000)*n^6 - (16449954386565250570953061/4927752910080000)*n^5 + (221918565946263316887085993/5807708786880000)*n^4 - (10957734288074023213947593/32265048816000)*n^3 + (2862432967014430147953611/1301923022400)*n^2 - (2468325092191770300413/267711444)*n + 18791509421817 for n>31