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 A241872 #26 Jul 14 2015 10:58:17
%S A241872 4,53,429,2748,15342,78339,376159,1728458,7689744,33393393,142376385,
%T A241872 598555320,2489143090,10264270175,42048021027,171366151974,
%U A241872 695585112660,2814484154445,11359684937605,45759869226260,184050366838134,739376299832763,2967455421451239
%N A241872 Number of ascent sequences of length n with exactly two descents.
%H A241872 Joerg Arndt and Alois P. Heinz, <a href="/A241872/b241872.txt">Table of n, a(n) for n = 5..1000</a>
%H A241872 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (17,-121,467,-1054,1388,-984,288).
%F A241872 G.f.: -(12*x^2-15*x+4)*x^5/((4*x-1)*(x-1)*(3*x-1)^2*(2*x-1)^3).
%F A241872 a(n) = 4^n/6 - 3^(n-1)*(2*n+1)/4 + 2^(n-4)*(n+2)*(n-1) + 1/12. - _Vaclav Kotesovec_, May 03 2014
%F A241872 Recurrence: a(n) = 288*a(n-7) - 984*a(n-6) + 1388*a(n-5) - 1054*a(n-4) + 467*a(n-3) - 121*a(n-2) + 17*a(n-1). - _Fung Lam_, May 05 2014
%p A241872 gf := -(12*x^2-15*x+4)*x^5/((4*x-1)*(x-1)*(3*x-1)^2*(2*x-1)^3):
%p A241872 a:= n-> coeff(series(gf, x, n+1), x, n):
%p A241872 seq(a(n), n=5..30);
%t A241872 CoefficientList[Series[-(12 x^2 - 15 x + 4)/((4 x - 1) (x - 1) (3 x - 1)^2 (2 x - 1)^3), {x, 0, 40}], x] (* _Vincenzo Librandi_, May 06 2014 *)
%t A241872 LinearRecurrence[{17,-121,467,-1054,1388,-984,288},{4,53,429,2748,15342,78339,376159},23] (* _Ray Chandler_, Jul 14 2015 *)
%Y A241872 Column k=2 of A238858.
%K A241872 nonn,easy
%O A241872 5,1
%A A241872 _Joerg Arndt_ and _Alois P. Heinz_, Apr 30 2014