Largest prime < a nontrivial power of a prime.

Terms

a(0) =3a(1) =7a(2) =7a(3) =13a(4) =23a(5) =23a(6) =31a(7) =47a(8) =61a(9) =79a(10) =113a(11) =113a(12) =127a(13) =167a(14) =241a(15) =251a(16) =283a(17) =337a(18) =359a(19) =509a(20) =523a(21) =619a(22) =727a(23) =839a(24) =953a(25) =1021a(26) =1327a(27) =1367a(28) =1669a(29) =1847