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 A091682 #35 Feb 16 2025 08:32:52
%S A091682 1,7,3,6,3,9,9,8,5,8,7,1,8,7,1,5,0,7,7,9,0,9,7,9,5,1,6,8,3,6,4,9,2,3,
%T A091682 4,9,6,0,6,3,1,2,5,8,3,2,9,0,9,4,9,7,9,0,5,6,8,2,1,9,6,6,5,2,3,0,8,4,
%U A091682 7,1,8,1,8,0,2,8,0,7,8,6,4,0,8,1,8,6,9,4,4,4,1,8,2,4,9,0,2,2,5,9,7,4
%N A091682 Decimal expansion of 2*(18 + sqrt(3)*Pi)/27.
%C A091682 Also, decimal expansion of Sum_{h >= 0} 1/binomial(2*h,h). [From Renzo Sprugnoli]
%H A091682 Michael Penn, <a href="https://www.youtube.com/watch?v=FELsk-PrVpU">So many factorials!!!</a>, YouTube video, 2020.
%H A091682 Renzo Sprugnoli, <a href="http://www.emis.de/journals/INTEGERS/papers/g27/g27.Abstract.html">Sums of Reciprocals of the Central Binomial Coefficients</a>, INTEGERS, 6 (2006), #A27, page 9.
%H A091682 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FactorialSums.html">Factorial Sums</a>
%H A091682 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F A091682 Sum_{n>=0} (n!)^2/(2n)!.
%F A091682 Equals A073016 plus 1. - _R. J. Mathar_, Sep 08 2008
%e A091682 1.736399858718715077909795168364923496063125832909497905682196652308471818...
%t A091682 RealDigits[N[(2 (18 + Pi Sqrt@3))/27, 120]] // First (* _Michael De Vlieger_, Sep 11 2015 *)
%o A091682 (PARI) default(realprecision,2000); 2*(18 + sqrt(3)*Pi)/27 \\ _Anders Hellström_, Sep 11 2015
%Y A091682 Cf. A248179: decimal expansion of Sum_{h >= 0} 1/binomial(2*h+1,h).
%K A091682 nonn,cons
%O A091682 1,2
%A A091682 _Eric W. Weisstein_, Jan 28 2004