a(n) = 6^n-prevprime(6^n).

Terms

a(0) =1a(1) =5a(2) =5a(3) =5a(4) =17a(5) =7a(6) =17a(7) =7a(8) =7a(9) =7a(10) =59a(11) =19a(12) =17a(13) =13a(14) =7a(15) =19a(16) =49a(17) =13a(18) =19a(19) =7a(20) =23a(21) =35a(22) =19a(23) =89a(24) =17a(25) =119a(26) =29a(27) =55a(28) =5a(29) =19