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 A347909 #20 Oct 03 2021 05:37:00
%S A347909 7,4,6,8,2,4,1,3,2,8,1,2,4,2,7,0,2,5,3,9,9,4,6,7,4,3,6,1,3,1,8,5,3,0,
%T A347909 0,5,3,5,4,4,9,9,6,8,6,8,1,2,6,0,6,3,2,9,0,2,7,6,5,4,4,9,8,9,5,8,6,0,
%U A347909 5,3,2,7,5,6,1,7,7,2,8,3,1,4,9,7,8,4,8,4,2,9,8
%N A347909 Decimal expansion of Integral_{x=0..1} exp(-x^2) dx.
%F A347909 Equals (sqrt(Pi)/2) * erf(1) = (sqrt(Pi)/(2*i)) * erfi(i).
%F A347909 Equals Sum_{k>=0} (-1)^k / ((2*k + 1)*k!). - _Ilya Gutkovskiy_, Sep 18 2021
%e A347909 0.74682413281242702539946743613185300535449968...
%t A347909 RealDigits[(Sqrt[Pi]/2) Erf[1], 10, 91][[1]]
%o A347909 (PARI) intnum(x=0, 1, exp(-x^2)) \\ _Michel Marcus_, Sep 18 2021
%Y A347909 Cf. A019704 (sqrt(Pi)/2 = Integral_{x=0..+oo} exp(-x^2) dx), A002161 (sqrt(Pi) = Integral_{x=-oo..+oo} exp(-x^2) dx).
%Y A347909 Cf. A347910 (inverse integrand), A007680.
%K A347909 nonn,easy,cons
%O A347909 0,1
%A A347909 _Jianing Song_, Sep 18 2021