Primes formed by concatenating k with k+1, where k+1 is a prime.

Terms

a(0) =23a(1) =67a(2) =1213a(3) =3637a(4) =4243a(5) =7879a(6) =9697a(7) =102103a(8) =108109a(9) =126127a(10) =138139a(11) =150151a(12) =156157a(13) =180181a(14) =192193a(15) =270271a(16) =276277a(17) =312313a(18) =330331a(19) =378379a(20) =420421a(21) =432433a(22) =438439a(23) =456457a(24) =522523a(25) =540541a(26) =546547a(27) =576577a(28) =600601a(29) =606607