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 A291893 #8 Sep 09 2017 11:37:07 %S A291893 1,9,89,639,4082,23191,122381,607944,2887756,13229876,58898404, %T A291893 256121253,1092452270,4585149401,18985099139,77707979700,314944855135, %U A291893 1265638606115,5048705160315,20010229736469,78861912700117,309252947330313,1207359268831473 %N A291893 Number of symmetrically unique Dyck paths of semilength n and height nine. %H A291893 Alois P. Heinz, <a href="/A291893/b291893.txt">Table of n, a(n) for n = 9..1000</a> %H A291893 <a href="/index/Rec#order_18">Index entries for linear recurrences with constant coefficients</a>, signature (18, -129, 428, -339, -2154, 7022, -5004, -13608, 31128, -13587, -27364, 38529, -11230, -11610, 11180, -3805, 550, -25). %F A291893 G.f.: -x^9*(-1+9*x-56*x^2+230*x^3-548*x^4+741*x^5-564*x^6+238*x^7-55*x^8+5*x^9) / ((x^2-3*x+1) *(5*x^2-5*x+1) *(5*x^4-5*x^2+1) *(x^5-3*x^4-3*x^3+4*x^2+x-1) *(x^5-15*x^4+35*x^3-28*x^2+9*x-1)). %Y A291893 Column k=9 of A291883. %K A291893 nonn,easy %O A291893 9,2 %A A291893 _Alois P. Heinz_, Sep 05 2017