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 A287220 #14 Jun 13 2017 09:16:33 %S A287220 0,0,1,4,10,36,85,312,737,2760,6604,25176 %N A287220 Number of single-crossing partitions on n nodes. %C A287220 The meandric numbers A005316 are the numbers of paths which cross themselves 0 times. %C A287220 This sequence is the number of paths that must cross themselves exactly once. %H A287220 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 A287220 a(2) = 1, this is from the partition (2,1). %e A287220 a(3) = 4, this is from the partitions (1,3,2),(2,1,3),(2,3,1),(3,1,2). %Y A287220 Cf. A005316, A287221. %K A287220 nonn,more %O A287220 0,4 %A A287220 _Benedict W. J. Irwin_, May 22 2017