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 A246820 #13 Jan 17 2020 16:07:35
%S A246820 3,4,3,3,7,7,9,6,1,5,5,6,4,2,7,0,3,2,8,3,2,5,3,3,0,0,3,8,5,8,3,1,2,4,
%T A246820 3,4,0,0,1,2,4,4,0,1,9,4,9,9,9,0,7,5,1,9,2,0,5,7,6,7,1,8,1,6,3,8,7,0,
%U A246820 4,6,4,2,2,9,8,1,1,7,5,7,2,6,2,8,3,3,3,2,7,6,2,9,6,8,6,0,1,2,1,2,4,5,5,1
%N A246820 Decimal expansion of integral_{0..infinity} x*exp(-x)/(1+x^2) dx.
%H A246820 Steven R. Finch, <a href="http://arxiv.org/abs/2001.00578">Errata and Addenda to Mathematical Constants</a>, p. 52.
%F A246820 (1/2)*sin(1)*(Pi - 2*Si(1)) - cos(1)*Ci(1), where Si is the sine integral function and Ci the cosine integral function.
%F A246820 Also equals -integral_{0..1} log(x)/(1+log(x)^2) dx.
%F A246820 Also equals cot(1)*A224518 + Ci(1)*csc(1).
%e A246820 0.3433779615564270328325330038583124340012440194999075192...
%t A246820 RealDigits[(1/2)*Sin[1]*(Pi - 2*SinIntegral[1]) - Cos[1]*CosIntegral[1], 10, 104] // First
%Y A246820 Cf. A073447, A073449, A099281, A099282, A224518.
%K A246820 nonn,cons,easy
%O A246820 0,1
%A A246820 _Jean-François Alcover_, Sep 04 2014