Concatenation of 'prevprime(k) and k and prevprime(k)' is a prime.

Terms

a(0) =5a(1) =8a(2) =9a(3) =12a(4) =14a(5) =17a(6) =19a(7) =23a(8) =25a(9) =28a(10) =31a(11) =33a(12) =38a(13) =39a(14) =41a(15) =42a(16) =47a(17) =48a(18) =51a(19) =60a(20) =61a(21) =62a(22) =63a(23) =69a(24) =71a(25) =72a(26) =75a(27) =77a(28) =78a(29) =80