Primes formed from the concatenation of previousprime(n) and n.

Terms

a(0) =23a(1) =79a(2) =3137a(3) =3739a(4) =4751a(5) =6163a(6) =8387a(7) =8389a(8) =109111a(9) =113117a(10) =113123a(11) =151153a(12) =151157a(13) =157163a(14) =167173a(15) =173177a(16) =181183a(17) =199207a(18) =199211a(19) =211213a(20) =211217a(21) =211219a(22) =233239a(23) =241249a(24) =251257a(25) =257263a(26) =263267a(27) =263269a(28) =271273a(29) =271277