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 A048408 #5 Oct 10 2019 23:18:06 %S A048408 0,1,2,3,4,5,6,7,8,9,17,28,39,60,71,82,93,171,282,393,606,717,828,939, %T A048408 1717,2828,3939,6060,7171,8282,9393,17171,28282,39393,60606,71717, %U A048408 82828,93939,171717,282828,393939,606060,717171,828282,939393,1717171 %N A048408 Numbers whose consecutive digits differ by 6. %Y A048408 Cf. A033075, A033088, A033081, A048407-A048410. %K A048408 nonn,base %O A048408 0,3 %A A048408 _Patrick De Geest_, Apr 15 1999