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 A006220 M2866 #15 Jul 08 2025 16:43:55 %S A006220 1,1,3,10,45,251,1638,12300,104877,1000135,10534062,121436206, %T A006220 1521332904 %N A006220 From descending subsequences of permutations. %D A006220 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006220 S. Pilpel, <a href="http://dx.doi.org/10.1016/0097-3165(90)90022-O">Descending subsequences of random permutations</a>, J. Combin. Theory, A 53 (1990), 96-116. %Y A006220 Diagonal of A224652. %K A006220 nonn,more %O A006220 1,3 %A A006220 _N. J. A. Sloane_ %E A006220 a(11)-a(13) from _Sean A. Irvine_, Feb 03 2017