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 A271924 #11 Nov 30 2017 08:04:06
%S A271924 1,3,13,19,285,465,17205,147963,345247,11137,291153,175741,12829093,
%T A271924 494964309,494964309,919219431,6858791139,706455487317,77003648117553,
%U A271924 1262354887173,1262354887173,26321041453443,500099787615417,952244801075931,50118147425049,95795446344081
%N A271924 Denominator of (1/3)*(Product_{j=0..n-1} (((2*j+1)*(3*j+4))/((j+1)*(6*j+1))) - 1).
%H A271924 J. de Gier, <a href="http://arXiv.org/abs/math.CO/0211285">Loops, matchings and alternating-sign matrices</a>, arXiv:math.CO/0211285, 2002.
%e A271924 1, 5/3, 29/13, 52/19, 913/285, 1693/465, 69769/17205, 658529/147963, 1667651/ 345247, 57873/11137, 1616141/291153, 1035959/175741, 79918969/12829093, ...
%p A271924 f3:=proc(n) local j;
%p A271924 (1/3)*(mul(((2*j+1)*(3*j+4))/((j+1)*(6*j+1)),j=0..n-1)-1); end;
%p A271924 t3:=[seq(f3(n),n=1..50)];
%p A271924 map(numer,t3);
%p A271924 map(denom,t3);
%t A271924 a[n_] := (1/3)*(Product[((2*j + 1)*(3*j + 4))/((j + 1)*(6*j + 1)), {j, 0, n - 1}] - 1) // Denominator;
%t A271924 Array[a, 26] (* _Jean-François Alcover_, Nov 30 2017 *)
%Y A271924 Sequences of fractions from de Gier paper: A271919-A271926.
%K A271924 nonn,frac
%O A271924 1,2
%A A271924 _N. J. A. Sloane_, May 04 2016