a(n) = ceiling(6^n/n).

Terms

a(0) =6a(1) =18a(2) =72a(3) =324a(4) =1556a(5) =7776a(6) =39991a(7) =209952a(8) =1119744a(9) =6046618a(10) =32981551a(11) =181398528a(12) =1004668771a(13) =5597440293a(14) =31345665639a(15) =176319369216a(16) =995685849691