A quick analysis of the sequence shows that the second differences of the log(a(n)) is constant : 2.1809815915841... which I can't identify now, being away from my tables and programs. The sequence is : [1, 57, 12675, 24318165, 414295148741, 62567386502084877, 83677847847984287628595, 990966953618170260281935463385, 103919148791293834318983090438798793469, 96498428501909654589630887978835098088148177857, 793474866816582266820936671790189132321673383112185151899, 57774258489513238998237970307483999327287210756991189655942651331169, 372497923\ 07686396442294904767024517674249157948208717533254799550970595875237705, 212667\ 7329003662242497893576504405980988058610832691271966238722132281963524554475750\ 29701325, 107514643083613831187684137548661238097337888203278444027646016628708\ 83601711298309339239868998337801509491, 481306696382275541642905602248429964648\ 6874100967249263944719599975607459850502222039591149331431805524655467453067042\ 377, 19079388919628199204605726181850465220151058338147922243967269231944059187\ 214767997105992341735209230667288462179090073659712583262087437, 66972311428882\ 9212892740188841706543509937780640178732810318337696945624428547218105214326012\ 774371397184848890970111836283470468812827907149926502347633] A094777 (not updated yet). Best regards, Simon Plouffe