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 A383770 #21 Jun 16 2025 23:35:29 %S A383770 1,1,4,17,77,367,1815,9233,48014,254123,1364491,7414733,40701346, %T A383770 225359021,1257148285,7058816337,39863261170,226270553575, %U A383770 1290212119208,7387057794679,42450966727899,244771835135261,1415678529391032,8210790845555365,47744558865042855 %N A383770 Number of nonnesting permutations of [n] avoiding 231 (and by symmetry 132, 213, or 312). %H A383770 K. Archer and R. P. Laudone, <a href="https://arxiv.org/abs/2502.13309">Pattern avoidance in non-crossing and non-nesting permutations</a>, arXiv:2502.13309 [math.CO], 2025. %F A383770 G.f.: A(x) satisfies x^3*A(x)^3 - (x^3+3*x^2+x)*A(x)^2 + (2*x^2-x+1)*A(x) + x - 1 = 0. %Y A383770 Cf. A383771. %K A383770 nonn %O A383770 0,3 %A A383770 _Robert P. Laudone_, May 09 2025