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 A005680 M0403 #16 Nov 09 2020 00:01:02 %S A005680 1,2,3,1,2,1,3,2,3,1,3,2,1,2,3,1,2,1,3,2,1,2,3,1,3,2,3,1,2,1,3,2,3,1, %T A005680 3,2,1,2,3,1,3,2,3,1,2,1,3,2,1,2,3,1,2,1,3,2,3,1,3,2,1,2,3,1,2,1,3,2, %U A005680 1,2,3,1,3,2,3,1,2,1,3 %N A005680 A squarefree ternary sequence. %D A005680 G. Siebert, personal communication. %D A005680 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A005680 Sean A. Irvine, <a href="/A005680/b005680.txt">Table of n, a(n) for n = 1..10000</a> %H A005680 G. Siebert, <a href="/A001285/a001285_1.pdf">Letter to N. J. A. Sloane, Sept. 1977</a> %Y A005680 Cf. A036582 (apparently essentially the same sequence). %K A005680 nonn %O A005680 1,2 %A A005680 _N. J. A. Sloane_