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 A373507 #18 Jun 10 2024 03:44:07
%S A373507 1,9,7,7,0,0,1,0,5,9,6,0,9,6,3,6,9,1,5,6,7,6,5,3,6,2,3,7,2,6,3,0,7,3,
%T A373507 7,7,9,5,2,6,5,5,6,2,5,3,1,7,8,7,6,5,7,0,7,3,8,3,5,2,5,1,0,7,6,8,6,4,
%U A373507 6,1,3,6,4,7,8,9,4,1,0,1,9,3,8,5,9,7
%N A373507 Decimal expansion of 1/2 - sqrt(3)*Pi/18.
%H A373507 Renzo Sprugnoli, <a href="https://www.emis.de/journals/INTEGERS/papers/g27/g27.Abstract.html">Sums of reciprocals of the central binomial coefficients</a>, INTEGERS 6 (2006) #A27.
%F A373507 Equals Sum_{n>=2} 1/((n-1)*binomial(2n,n)).
%F A373507 Sum_{n>=2} (-1)^n/((n-1)*binomial(2n,n)) = 3*log(phi)/sqrt(5) - 1/2 = 0.145613... where phi is the golden ratio.
%e A373507 0.1977001059609636915676536237263...
%p A373507 1/2-sqrt(3)*Pi/18; evalf(%) ;
%t A373507 RealDigits[1/2 - Sqrt[3]*Pi/18, 10, 120][[1]] (* _Amiram Eldar_, Jun 10 2024 *)
%o A373507 (PARI) 1/2 - sqrt(3)*Pi/18 \\ _Amiram Eldar_, Jun 10 2024
%Y A373507 Cf. A373508 (denominator (n-1)^2), A373506 (denominator n+1), A073010 (denominator n).
%K A373507 nonn,cons
%O A373507 0,2
%A A373507 _R. J. Mathar_, Jun 07 2024