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 A048315 #7 Oct 13 2019 16:36:07 %S A048315 0,1,2,3,5,10,15,20,21,22,23,40,41,42,43,60,61,62,63,84,85,86,87,168, %T A048315 169,170,171,252,253,254,255,336,340,341,342,343,346,351,672,677,680, %U A048315 681,682,683,687,1008,1013,1018,1020,1021,1022,1023,1345,1346,1347 %N A048315 Numbers whose base-4 expansions, read from left to right, have run lengths that strictly decrease. %Y A048315 Cf. A037013, A043693, A043707, A044815, A044953. %K A048315 nonn,base %O A048315 0,3 %A A048315 _Patrick De Geest_, Feb 15 1999