a(n) = 7^n + 7*n.

Terms

a(0) =1a(1) =14a(2) =63a(3) =364a(4) =2429a(5) =16842a(6) =117691a(7) =823592a(8) =5764857a(9) =40353670a(10) =282475319a(11) =1977326820a(12) =13841287285a(13) =96889010498a(14) =678223072947