Powers of 7: a(n) = 7^n.

Terms

a(0) =1a(1) =7a(2) =49a(3) =343a(4) =2401a(5) =16807a(6) =117649a(7) =823543a(8) =5764801a(9) =40353607a(10) =282475249a(11) =1977326743a(12) =13841287201a(13) =96889010407a(14) =678223072849