a(n) = 6^n - n^5.

Terms

a(0) =1a(1) =5a(2) =4a(3) =-27a(4) =272a(5) =4651a(6) =38880a(7) =263129a(8) =1646848a(9) =10018647a(10) =60366176a(11) =362636005a(12) =2176533504a(13) =13060322723a(14) =78363626272a(15) =470184225201