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 A116715 #9 Oct 20 2017 14:36:54 %S A116715 1,2,5,12,25,54,120,265,580,1272,2796,6143,13488,29619,65053,142873, %T A116715 313771,689095,1513390,3323699,7299465,16031000,35207128,77321545, %U A116715 169812767,372941033,819049274,1798787604,3950478790,8676000808,19054143661,41846514135 %N A116715 Number of permutations of length n which avoid the patterns 312, 2341, 4321. %H A116715 Colin Barker, <a href="/A116715/b116715.txt">Table of n, a(n) for n = 1..1000</a> %H A116715 Lara Pudwell, <a href="http://faculty.valpo.edu/lpudwell/maple/webbook/bookmain.html">Systematic Studies in Pattern Avoidance</a>, 2005. %H A116715 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,2,3,1). %F A116715 G.f.: x*(1 + x)*(1 + 2*x^2 + x^3) / (1 - x - x^2 - 2*x^3 - 3*x^4 - x^5). %F A116715 a(n) = a(n-1) + a(n-2) + 2*a(n-3) + 3*a(n-4) + a(n-5) for n>5. - _Colin Barker_, Oct 20 2017 %o A116715 (PARI) Vec(x*(1 + x)*(1 + 2*x^2 + x^3) / (1 - x - x^2 - 2*x^3 - 3*x^4 - x^5) + O(x^40)) \\ _Colin Barker_, Oct 20 2017 %K A116715 nonn,easy %O A116715 1,2 %A A116715 _Lara Pudwell_, Feb 26 2006