Empirical for n mod 6 = 0: a(n) = (1/14311272528885177990144000000)*n^25 + (13/396312162338358775111680000)*n^24 + (2699/368004150742761719746560000)*n^23 + (143029/112001263269536175575040000)*n^22 + (52414361/305457990735098660659200000)*n^21 + (49086409/2909123721286653911040000)*n^20 + (239472973/195806404317370936320000)*n^19 + (56657201239/803836817723943843840000)*n^18 + (13814941801/4093897722047078400000)*n^17 + (767034582131/5731456810865909760000)*n^16 + (502646761133239/115584379019129180160000)*n^15 + (686711941737001/5504018048529960960000)*n^14 + (401408747680854919/128427087799032422400000)*n^13 + (42745713443329397/658600450251448320000)*n^12 + (10471871376509401/9266023650723840000)*n^11 + (222406854342485383/10810360925844480000)*n^10 + (41538154452919377641/153146779782796800000)*n^9 + (8729260459575866957/2917081519672320000)*n^8 + (4197015355087079447/113045408542080000)*n^7 + (30404130911387989517/122465859253920000)*n^6 + (93753661767512415744091/35281830880296000000)*n^5 + (652100989375218812249/219531392144064000)*n^4 + (56821757437447018308541/140256167203152000)*n^3 - (65955580587160618931/15902059773600)*n^2 + (44982123308809307/2362159800)*n + 23788880 for n>18
Empirical for n mod 6 = 1: a(n) = (1/14311272528885177990144000000)*n^25 + (13/396312162338358775111680000)*n^24 + (2699/368004150742761719746560000)*n^23 + (143029/112001263269536175575040000)*n^22 + (52414361/305457990735098660659200000)*n^21 + (49086409/2909123721286653911040000)*n^20 + (239472973/195806404317370936320000)*n^19 + (56657201239/803836817723943843840000)*n^18 + (13814941801/4093897722047078400000)*n^17 + (767034582131/5731456810865909760000)*n^16 + (502646761133239/115584379019129180160000)*n^15 + (686711941737001/5504018048529960960000)*n^14 + (401408747680854919/128427087799032422400000)*n^13 + (10387208368402099471/160039909411101941760000)*n^12 + (77111052990628571/68231628700784640000)*n^11 + (162134636185756998607/7880753114940625920000)*n^10 + (272532363207618510472601/1004796022154929804800000)*n^9 + (57271431451793193340877/19138971850570091520000)*n^8 + (82599679790892947540201/2225072776333760640000)*n^7 + (898393056739215340169879/3615743261542361040000)*n^6 + (16630078513133941406276332127/6250070494951795512000000)*n^5 + (1026850711722608312607142627/350003947717300548672000)*n^4 + (2444478462019972969891365112651/6037568098123434464592000)*n^3 - (8511407767368989278784652137/2053594591198447096800)*n^2 + (5784444246202854395211931/305049701604047400)*n - (818436516783615221/94143178827) for n>18
Empirical for n mod 6 = 2: a(n) = (1/14311272528885177990144000000)*n^25 + (13/396312162338358775111680000)*n^24 + (2699/368004150742761719746560000)*n^23 + (143029/112001263269536175575040000)*n^22 + (52414361/305457990735098660659200000)*n^21 + (49086409/2909123721286653911040000)*n^20 + (239472973/195806404317370936320000)*n^19 + (56657201239/803836817723943843840000)*n^18 + (13814941801/4093897722047078400000)*n^17 + (767034582131/5731456810865909760000)*n^16 + (502646761133239/115584379019129180160000)*n^15 + (686711941737001/5504018048529960960000)*n^14 + (401408747680854919/128427087799032422400000)*n^13 + (10387208366732493071/160039909411101941760000)*n^12 + (2544664745848776443/2251643747125893120000)*n^11 + (54044863271080136069/2626917704980208640000)*n^10 + (272531893337644967502601/1004796022154929804800000)*n^9 + (57272898879849080734477/19138971850570091520000)*n^8 + (82608675423033534795301/2225072776333760640000)*n^7 + (224311761230426077856651/903935815385590260000)*n^6 + (16590398824449989615057838377/6250070494951795512000000)*n^5 + (1052489188261734650718987247/350003947717300548672000)*n^4 + (2447071333166299150419645294361/6037568098123434464592000)*n^3 - (22519280460174848966776361/5432789923805415600)*n^2 + (26000943222645528361185457/1372723657218213300)*n + (2222552859014937112/94143178827) for n>18
Empirical for n mod 6 = 3: a(n) = (1/14311272528885177990144000000)*n^25 + (13/396312162338358775111680000)*n^24 + (2699/368004150742761719746560000)*n^23 + (143029/112001263269536175575040000)*n^22 + (52414361/305457990735098660659200000)*n^21 + (49086409/2909123721286653911040000)*n^20 + (239472973/195806404317370936320000)*n^19 + (56657201239/803836817723943843840000)*n^18 + (13814941801/4093897722047078400000)*n^17 + (767034582131/5731456810865909760000)*n^16 + (502646761133239/115584379019129180160000)*n^15 + (686711941737001/5504018048529960960000)*n^14 + (401408747680854919/128427087799032422400000)*n^13 + (42745713443329397/658600450251448320000)*n^12 + (10471871376509401/9266023650723840000)*n^11 + (222406854342485383/10810360925844480000)*n^10 + (41538154452919377641/153146779782796800000)*n^9 + (8729260459575866957/2917081519672320000)*n^8 + (4197015355087079447/113045408542080000)*n^7 + (30404130911387989517/122465859253920000)*n^6 + (93753661767512415744091/35281830880296000000)*n^5 + (652100989375218812249/219531392144064000)*n^4 + (56821757437447018308541/140256167203152000)*n^3 - (65955580587160618931/15902059773600)*n^2 + (44982123308809307/2362159800)*n - 9032561 for n>18
Empirical for n mod 6 = 4: a(n) = (1/14311272528885177990144000000)*n^25 + (13/396312162338358775111680000)*n^24 + (2699/368004150742761719746560000)*n^23 + (143029/112001263269536175575040000)*n^22 + (52414361/305457990735098660659200000)*n^21 + (49086409/2909123721286653911040000)*n^20 + (239472973/195806404317370936320000)*n^19 + (56657201239/803836817723943843840000)*n^18 + (13814941801/4093897722047078400000)*n^17 + (767034582131/5731456810865909760000)*n^16 + (502646761133239/115584379019129180160000)*n^15 + (686711941737001/5504018048529960960000)*n^14 + (401408747680854919/128427087799032422400000)*n^13 + (10387208368402099471/160039909411101941760000)*n^12 + (77111052990628571/68231628700784640000)*n^11 + (162134636185756998607/7880753114940625920000)*n^10 + (272532363207618510472601/1004796022154929804800000)*n^9 + (57271431451793193340877/19138971850570091520000)*n^8 + (82599679790892947540201/2225072776333760640000)*n^7 + (898393056739215340169879/3615743261542361040000)*n^6 + (16630078513133941406276332127/6250070494951795512000000)*n^5 + (1026850711722608312607142627/350003947717300548672000)*n^4 + (2444478462019972969891365112651/6037568098123434464592000)*n^3 - (8511407767368989278784652137/2053594591198447096800)*n^2 + (5784444246202854395211931/305049701604047400)*n + (2271478272639214486/94143178827) for n>18
Empirical for n mod 6 = 5: a(n) = (1/14311272528885177990144000000)*n^25 + (13/396312162338358775111680000)*n^24 + (2699/368004150742761719746560000)*n^23 + (143029/112001263269536175575040000)*n^22 + (52414361/305457990735098660659200000)*n^21 + (49086409/2909123721286653911040000)*n^20 + (239472973/195806404317370936320000)*n^19 + (56657201239/803836817723943843840000)*n^18 + (13814941801/4093897722047078400000)*n^17 + (767034582131/5731456810865909760000)*n^16 + (502646761133239/115584379019129180160000)*n^15 + (686711941737001/5504018048529960960000)*n^14 + (401408747680854919/128427087799032422400000)*n^13 + (10387208366732493071/160039909411101941760000)*n^12 + (2544664745848776443/2251643747125893120000)*n^11 + (54044863271080136069/2626917704980208640000)*n^10 + (272531893337644967502601/1004796022154929804800000)*n^9 + (57272898879849080734477/19138971850570091520000)*n^8 + (82608675423033534795301/2225072776333760640000)*n^7 + (224311761230426077856651/903935815385590260000)*n^6 + (16590398824449989615057838377/6250070494951795512000000)*n^5 + (1052489188261734650718987247/350003947717300548672000)*n^4 + (2447071333166299150419645294361/6037568098123434464592000)*n^3 - (22519280460174848966776361/5432789923805415600)*n^2 + (26000943222645528361185457/1372723657218213300)*n - (867361930407892595/94143178827) for n>18