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 A116712 #17 Nov 29 2018 10:35:12
%S A116712 1,2,5,12,27,59,126,265,551,1136,2327,4743,9630,19493,39363,79336,
%T A116712 159659,320915,644414,1293009,2592783,5196512,10410735,20850127,
%U A116712 41746622,83568269,167257931,334712280,669742371,1339998971
%N A116712 Number of permutations of length n which avoid the patterns 231, 3214, 4312.
%H A116712 Michael Dairyko, Lara Pudwell, Samantha Tyner, Casey Wynn, <a href="http://www.combinatorics.org/ojs/index.php/eljc/article/view/v19i3p22">Non-contiguous pattern avoidance in binary trees</a>. Electron. J. Combin. 19 (2012), no. 3, Paper 22, 21 pp. MR2967227. - From _N. J. A. Sloane_, Feb 01 2013
%H A116712 Lara Pudwell, <a href="http://faculty.valpo.edu/lpudwell/maple/webbook/bookmain.html">Systematic Studies in Pattern Avoidance</a>, 2005.
%H A116712 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-1,-2).
%F A116712 G.f.: A(x) = (x^3-x+1)*x/((2*x-1)*(x^2+x-1)).
%F A116712 a(n) = A257113(n+1) - A000045(n+2). - _R. J. Mathar_, Nov 07 2017
%t A116712 CoefficientList[Series[(x^3-x+1)/((2*x-1)*(x^2+x-1)), {x, 0, 50}], x] (* _Stefano Spezia_, Nov 29 2018 *)
%K A116712 nonn,easy
%O A116712 1,2
%A A116712 _Lara Pudwell_, Feb 26 2006