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 A261921 #5 Sep 15 2015 15:52:04 %S A261921 12,13,14,15,16,17,18,19,20,23,24,25,26,27,28,29,30,31,34,35,36,37,38, %T A261921 39,40,41,42,45,46,47,48,49,50,51,52,53,56,57,58,59,60,61,62,63,64,67, %U A261921 68,69,70,71,72,73,74,75,78,79,80,81,82,83,84,85,86,89,90,91,92,93,94,95,96,97,100,101,102,103,104,105,106,107,108,112,122,123,132 %N A261921 Nonpalindromes which are the sum of two palindromes whose lengths differ by 1. %C A261921 More than the usual number of terms are displayed in order to show that this is different from A261907. %e A261921 12=11+1 and 100=99+1 are members. %e A261921 10 is not a member since it is only the sum of two palindromes (5+5) whose lengths are equal. %Y A261921 Cf. A002113. A subsequence of A261907. A261920 shows the differences. %K A261921 nonn,base %O A261921 1,1 %A A261921 _David Applegate_ and _N. J. A. Sloane_, Sep 15 2015