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 A287221 #12 Jun 13 2017 09:16:06 %S A287221 0,0,0,0,8,42,168,760,2418,10490,30842,131676 %N A287221 Number of twice-crossing partitions on n nodes. %C A287221 The meandric numbers A005316 are the numbers of paths which cross themselves 0 times. %C A287221 This sequence is the number of paths that must cross themselves exactly twice. %H A287221 B. W. J. Irwin, <a href="https://www.authorea.com/users/5445/articles/173040-on-the-number-of-k-crossing-partitions/_show_article">On the number of k-crossing partitions</a> %e A287221 a(4) = 8; this is from the partitions %e A287221 (2,1,4,3), (2,4,3,1), %e A287221 (3,2,4,1), (3,4,2,1), %e A287221 (4,1,3,2), (4,2,1,3), %e A287221 (4,2,3,1), (4,3,1,2). %Y A287221 Cf. A005316, A287220. %K A287221 nonn,more %O A287221 0,5 %A A287221 _Benedict W. J. Irwin_, May 22 2017