a(n) = 7^n + n.

Terms

a(0) =1a(1) =8a(2) =51a(3) =346a(4) =2405a(5) =16812a(6) =117655a(7) =823550a(8) =5764809a(9) =40353616a(10) =282475259a(11) =1977326754a(12) =13841287213a(13) =96889010420a(14) =678223072863