a(n) = 12^n + 1.

Terms

a(0) =2a(1) =13a(2) =145a(3) =1729a(4) =20737a(5) =248833a(6) =2985985a(7) =35831809a(8) =429981697a(9) =5159780353a(10) =61917364225a(11) =743008370689