Palindromes k such that k + 2 is also a palindrome.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =9a(8) =99a(9) =999a(10) =9999a(11) =99999a(12) =999999a(13) =9999999a(14) =99999999a(15) =999999999a(16) =9999999999a(17) =99999999999a(18) =999999999999