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 A261909 #5 Sep 09 2015 15:09:56 %S A261909 1,10,11,20,21,30,31,40,41,50,51,60,61,70,71,80,81,90,91,100,110,111, %T A261909 121,131,141,151,161,171,181,191,192,200,201,212,220,231,232,252,262, %U A261909 272,282,292,293,300,302,312,313,321 %N A261909 A261908(n)/9. %C A261909 Created in an attempt to understand A035137. It would be nice to have an independent definition of these numbers. %Y A261909 Cf. A261908, A035137. %K A261909 nonn,base %O A261909 1,2 %A A261909 _N. J. A. Sloane_, Sep 09 2015