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 A143657 #7 Jan 13 2024 10:44:46
%S A143657 1,1,2,5,12,32,95,301,1001,3495,12708,47932,186581,747619,3073207
%N A143657 Number of 4-noncrossing stack-free partial matching without 1-arcs.
%C A143657 This sequence is the second row of Jin and Reidys table, p. 15; the first row, number of 3-noncrossing stack-free partial matching without 1-arcs, is A132441.
%H A143657 Emma Y. Jin and Christian M. Reidys, <a href="http://arxiv.org/abs/0711.1405">RNA-LEGO: Combinatorial Design of Pseudoknot RNA</a>, arXiv:0711.1405 [q-bio.BM], 2007.
%F A143657 a(n) = C_4(n,h) = SUM[b=0..{h-1}](-1)^{h-b-1}{h-1 Choose b}{T}_4(h-2h+2b+2,b+1); where the T function is defined in Jin and Reidys.
%F A143657 Asymptotically a(n) ~ (1.217 * 10^7)*(n^(-21/2))*(3.0382^n).
%Y A143657 Cf. A132441.
%K A143657 nonn,more
%O A143657 1,3
%A A143657 _Jonathan Vos Post_, Aug 28 2008