Primes formed by concatenating n with n+1 and by concatenating n+2 with n+3.

Terms

a(0) =67a(1) =89a(2) =7879a(3) =8081a(4) =9091a(5) =9293a(6) =186187a(7) =188189a(8) =276277a(9) =278279a(10) =426427a(11) =428429a(12) =438439a(13) =440441a(14) =450451a(15) =452453a(16) =600601a(17) =602603a(18) =606607a(19) =608609a(20) =798799a(21) =800801a(22) =816817a(23) =818819a(24) =858859a(25) =860861a(26) =936937a(27) =938939a(28) =960961a(29) =962963