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 A371803 #14 Mar 29 2025 20:06:46
%S A371803 1,2,7,9,3,3,3,8,2,4,1,3,1,7,5,4,7,2,8,7,3,9,8,1,5,7,2,4,4,8,5,5,6,6,
%T A371803 3,5,6,1,1,1,3,3,0,6,7,4,0,7,2,5,7,8,8,3,8,8,4,9,4,5,3,6,1,7,4,1,4,9,
%U A371803 6,2,9,2,8,0,9,6,9,9,8,0,4,6,1,8,9,3
%N A371803 Decimal expansion of Sum_{k>=0} (-1)^k / (k^2 + 4).
%F A371803 Equals (1/8)*(1 + 2*Pi*csch(2*Pi)).
%F A371803 Equals 1/8 + Pi*exp(2*Pi)/(2*(exp(4*Pi) - 1)). - _Vaclav Kotesovec_, Apr 22 2024
%e A371803 0.1279333824131754728739815724485566356111330...
%t A371803 s = Re[N[Sum[(-1)^k/(k^2 + 4), {k, 0, Infinity}], 120]]
%t A371803 First[RealDigits[s]]
%Y A371803 Cf. A329085.
%K A371803 nonn,cons
%O A371803 0,2
%A A371803 _Clark Kimberling_, Apr 17 2024