a(n) = 5*8^n+1.

Terms

a(0) =6a(1) =41a(2) =321a(3) =2561a(4) =20481a(5) =163841a(6) =1310721a(7) =10485761a(8) =83886081a(9) =671088641a(10) =5368709121a(11) =42949672961a(12) =343597383681