a(n) = 6^n + 8^n + 9^n.

Terms

a(0) =3a(1) =23a(2) =181a(3) =1457a(4) =11953a(5) =99593a(6) =840241a(7) =7160057a(8) =61503553a(9) =531715913a(10) =4620992401a(11) =40333791257a(12) =353325795553