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 A046267 #7 Oct 10 2019 00:36:02 %S A046267 1,9,8,9,656,9,1441,969,7,9,44,313,282,828,767,94649,888,6996,999, %T A046267 2992,545,989,232,959,6336,7897987,989,969,5115,101,44,989,838,30903, %U A046267 838,858,47874,959,85658,2552,808,474,717,636,969,97479,721127,696,84748 %N A046267 Largest palindromic substring in 9^n. %Y A046267 Cf. A046275. %K A046267 nonn,base %O A046267 0,2 %A A046267 _Patrick De Geest_, Jun 15 1998