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 A056617 #36 Aug 15 2024 06:41:41
%S A056617 1,3,5,7,9,11,13,5,17,19,21,23,25,27,29,31,11,7,37,13,41,43,3,47,49,
%T A056617 17,53,55,57,59,61,9,65,67,23,71,73,75,11,79,81,83,17,29,89,13,31,19,
%U A056617 97,11,101,103,35,107,109,37,113,115,39,119,121,41,125
%N A056617 Denominator of binomial(2*n,n) / (2*n+1).
%C A056617 The numerators are given in A056616.
%H A056617 Michel Marcus, <a href="/A056617/b056617.txt">Table of n, a(n) for n = 0..2000</a>
%F A056617 a(n) = denominator(r(n)) with r(n) = binomial(2*n,n)/(2*n+1).
%F A056617 G.f. of r(n): 1/(2*sqrt(x))*arcsin(2*sqrt(x)). [_Vladimir Kruchinin_, May 31 2013]
%e A056617 The rationals r(n) begin: 1, 2/3, 6/5, 20/7, 70/9, 252/11, 924/13, 1144/5, 12870/17, ...
%t A056617 Table[Binomial[2 n, n]/(2 n + 1), {n, 0, 70}]//Denominator (* _Harvey P. Dale_, May 01 2019 *)
%o A056617 (Magma) [Denominator((Binomial (2*n, n)) / (2*n + 1)): n in [0..70]]; // _Vincenzo Librandi_, May 27 2019
%o A056617 (PARI) a(n) = denominator(binomial(2*n,n) / (2*n+1)); \\ _Michel Marcus_, May 27 2019
%Y A056617 Cf. A056616, A000108.
%K A056617 nonn,easy,frac
%O A056617 0,2
%A A056617 _N. J. A. Sloane_, Aug 28 2000