Primes of the form k*10^x + k + 1, where 0 < k < 9, x=0,1,2..

Terms

a(0) =3a(1) =5a(2) =7a(3) =11a(4) =13a(5) =17a(6) =23a(7) =67a(8) =89a(9) =607a(10) =809a(11) =2003a(12) =6007a(13) =8009a(14) =200003a(15) =2000003a(16) =8000009a(17) =20000003a(18) =600000007a(19) =6000000007