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 A258428 #16 Aug 10 2020 09:28:22
%S A258428 3,5,2,5,1,3,4,2,1,7,7,7,6,1,8,9,9,7,4,7,0,8,5,9,9,2,2,7,2,3,9,5,3,5,
%T A258428 0,0,3,5,9,4,5,2,7,5,0,2,1,9,3,9,6,4,0,5,4,3,7,8,1,2,0,3,3,2,0,5,7,2,
%U A258428 9,9,8,6,8,4,2,3,4,3,7,3,5,5,5,2,0,4,8,2,4,4,5,1,5,2,8,6,4,0,3,2,8,8,2,1,0
%N A258428 Decimal expansion of arctan(1/e).
%C A258428 The slope of the unique straight line passing through the origin which kisses the logarithmic function y=log(x), i.e., the angle (in radians) the tangent line subtends with the X axis. The kissing point coordinates are (e,1).
%H A258428 Stanislav Sykora, <a href="/A258428/b258428.txt">Table of n, a(n) for n = 0..2000</a>
%F A258428 Equals Integral_{x=1..oo} 1/(2*cosh(x)) dx. - _Amiram Eldar_, Aug 10 2020
%e A258428 0.35251342177761899747085992272395350035945275021939640543781203320...
%e A258428 In degrees:
%e A258428 20.1975312895726498111743461325943940876066625590453644638010046029...
%t A258428 RealDigits[ArcTan[Exp[-1]],10,105][[1]] (* _Vaclav Kotesovec_, Jun 02 2015 *)
%o A258428 (PARI) atan(1/exp(1))
%Y A258428 Cf. A001113, A257777, A248618.
%K A258428 nonn,cons
%O A258428 0,1
%A A258428 _Stanislav Sykora_, May 31 2015