Empirical: a(n) = (1/48569119454267387884339200000000)*n^36 + (1/179885627608397732904960000000)*n^35 + (431/555578436821588650229760000000)*n^34 + (6667/92512608484318834065408000000)*n^33 + (182057713/36983588707158814044979200000000)*n^32 + (845392979/3236064011876396228935680000000)*n^31 + (3491454367/312587545233221786271744000000)*n^30 + (1616190698333/4092055137598539747557376000000)*n^29 + (159635485958647/13550593093853949355622400000000)*n^28 + (3670999736154221/12195533784468554420060160000000)*n^27 + (687896629397/103114294038052577280000000)*n^26 + (2316097860261683/17868913969917295853568000000)*n^25 + (9759874930715808347/4377883922629737484124160000000)*n^24 + (3751101551168073611/109447098065743437103104000000)*n^23 + (107810401929620861/226598546719965708288000000)*n^22 + (298203704051876737/49439682920719790899200000)*n^21 + (649591032355130958559/9181655399562246881280000000)*n^20 + (716122326116917184893/918165539956224688128000000)*n^19 + (3054955659140738466850333/371168419527303830175744000000)*n^18 + (671619833036305976434663/7918259616582481710415872000)*n^17 + (278826935463548588895599801/321357938984678640844800000000)*n^16 + (391612753943892519452617409/44186716610393313116160000000)*n^15 + (38783232008837021001379146563/435554778016734086430720000000)*n^14 + (2845400952294444171161139239/3350421369359492972544000000)*n^13 + (433460118319051628371664775991/59482118513990998425600000000)*n^12 + (245934504861988635718370990641/4663938838028839649280000000)*n^11 + (976921796279558983213616821/3290256675858087936000000)*n^10 + (309887111637051269149377552307/266510790744505122816000000)*n^9 + (362281576050239730407277496310519/146193154658394542899200000000)*n^8 + (60302938282179332803034210623/261059204747133112320000000)*n^7 - (16319864200194727321295422510711/4673135562417956874240000000)*n^6 + (156287461519385862539235733094587/3855336838994814421248000000)*n^5 + (1830256360054301778168358249/38854490692817479680000)*n^4 - (1657207655247848023155260911/2622678121765179878400)*n^3 + (2893965362625692684430113/17345754773579232000)*n^2 + (26813381051766560099/10314539492400)*n - 2976998 for n>4