a(n) = 8^n-6^n+1^n.

Terms

a(0) =1a(1) =3a(2) =29a(3) =297a(4) =2801a(5) =24993a(6) =215489a(7) =1817217a(8) =15097601a(9) =124140033a(10) =1013275649a(11) =8227137537a(12) =66542694401a(13) =536695119873