%I #20 Oct 03 2021 05:37:00

%S 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 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 5,3,2,7,5,6,1,7,7,2,8,3,1,4,9,7,8,4,8,4,2,9,8

%N Decimal expansion of Integral_{x=0..1} exp(-x^2) dx.

%F Equals (sqrt(Pi)/2) * erf(1) = (sqrt(Pi)/(2*i)) * erfi(i).

%F Equals Sum_{k>=0} (-1)^k / ((2*k + 1)*k!). - _Ilya Gutkovskiy_, Sep 18 2021

%e 0.74682413281242702539946743613185300535449968...

%t RealDigits[(Sqrt[Pi]/2) Erf[1], 10, 91][[1]]

%o (PARI) intnum(x=0, 1, exp(-x^2)) \\ _Michel Marcus_, Sep 18 2021

%Y 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 Cf. A347910 (inverse integrand), A007680.

%K nonn,easy,cons

%O 0,1

%A _Jianing Song_, Sep 18 2021