a(n) = 6^n + n.

Terms

a(0) =1a(1) =7a(2) =38a(3) =219a(4) =1300a(5) =7781a(6) =46662a(7) =279943a(8) =1679624a(9) =10077705a(10) =60466186a(11) =362797067a(12) =2176782348a(13) =13060694029a(14) =78364164110a(15) =470184984591