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 A294764 #12 Nov 05 2021 10:01:32
%S A294764 1,1,2,6,21,73,247,821,2704,8868,29030,94960,310531,1015359,3319829,
%T A294764 10854379,35488838,116031978,379370276,1240362982,4055405209,
%U A294764 13259272613,43351600979,141739396705,463421329340,1515170329456,4953896123490,16196916164572,52956316947055,173142311541835
%N A294764 Number of permutations of [n] avoiding {2143, 3142, 1234}.
%H A294764 D. Callan, T. Mansour, <a href="http://arxiv.org/abs/1705.00933">Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns</a>, arXiv:1705.00933 [math.CO] (2017), Table 2 No 111.
%H A294764 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (7,-18,24,-19,9,-2).
%F A294764 4*a(n) = n+1-n^2 -A175005(n) +A175005(n+1), n>0. - _R. J. Mathar_, Nov 05 2021
%p A294764 ((x^3-2*x^2+3*x-1)^2)/((2*x^3-3*x^2+4*x-1)*(x-1)^3) ;
%p A294764 taylor(%,x=0,40) ;
%p A294764 gfun[seriestolist](%) ;
%K A294764 nonn,easy
%O A294764 0,3
%A A294764 _R. J. Mathar_, Nov 08 2017