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 A343469 #25 Apr 21 2021 11:59:56
%S A343469 9,8,0,8,5,4,2,7,4,5,9,1,3,5,0,6,1,5,3,9,2,2,3,2,2,7,8,2,9,9,0,1,9,6,
%T A343469 2,2,1,1,8,5,4,1,8,0,0,7,2,0,2,3,2,0,3,6,0,6,9,7,9,0,4,2,6,4,1,3,8,8,
%U A343469 6,4,9,3,6,2,7,7,1,9,2,0,0,7,4,3,6,1,0,6,5,8,7,1
%N A343469 Decimal expansion of Sum_{n>=1} (-1)^(n-1)/(n*arctan(n)).
%C A343469 The alternating series test shows this series is convergent.
%H A343469 Wikipedia, <a href="https://en.wikipedia.org/wiki/Alternating_series_test">Alternating series test</a>.
%F A343469 Equals Sum_{n>=1} (-1)^(n-1)/(n*arctan(n)).
%e A343469 0.98085427459135061539223227829901962211854180072023203606979...
%p A343469 evalf(sum((-1)^(n-1)/(n*arctan(n)), n=1..infinity),120);
%o A343469 (PARI) sumalt(n=1, (-1)^(n-1)/(n*atan(n))) \\ _Michel Marcus_, Apr 16 2021
%Y A343469 Cf. A343470, A265011.
%K A343469 nonn,cons
%O A343469 0,1
%A A343469 _Bernard Schott_, Apr 16 2021