This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A337880 #20 Sep 30 2020 14:56:14 %S A337880 1,2,3,4,5,6,10,19,28,17,48,7,18,38,16,27,47,8,30,41,52,63,83,50,15, %T A337880 26,37,46,9,20,31,42,53,64,73,40,51,62,93,60,14,25,36,56,12,23,34,45, %U A337880 65,21,32,43,54,74,72,61,102,90,11,22,33,44,55,66,57,13,24,35,67,49,29,84,71 %N A337880 Lexicographically earliest sequence of distinct positive integers such that the sum of a(n) and [a(n+1) reversed] is a palindrome in base 10 (terms ending in zero permitted). %C A337880 Terms ending in zero are permitted; when they are reversed, the leading zero(s) is (are) erased. %H A337880 Carole Dubois, <a href="/A337880/b337880.txt">Table of n, a(n) for n = 1..5001</a> %e A337880 a(6) = 6 and a(7) = 10; the addition 6 + (0)1 is a palindrome (7). %e A337880 a(7) = 10 and a(8) = 19; the addition 10 + 91 is a palindrome (101). %e A337880 a(8) = 19 and a(9) = 28; the addition 19 + 82 is a palindrome (101). Etc. %Y A337880 Cf. A337865 (no term ending in zero is permitted). %K A337880 nonn,base,look %O A337880 1,2 %A A337880 _Eric Angelini_ and _Carole Dubois_, Sep 28 2020