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 A055504 #9 Jun 17 2017 03:55:03 %S A055504 0,0,0,0,0,15,110,455,1400,3570,7980,16170,30360,53625,90090,145145, %T A055504 225680,340340,499800,717060,1007760,1390515,1887270,2523675,3329480, %U A055504 4338950,5591300,7131150,9009000,11281725,14013090,17274285,21144480 %N A055504 n*(n-1)*(n-2)*(n-3)*(n-4)*(2*n-1)/72. %D A055504 L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 73, Problem 3. %H A055504 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (7,-21,35,-35,21,-7,1). %F A055504 G.f.: 5*x^5*(3+x)/(1-x)^7. [_Colin Barker_, May 09 2012] %K A055504 nonn,easy %O A055504 0,6 %A A055504 _N. J. A. Sloane_, Jul 10 2000