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 A125961 #34 May 07 2025 16:55:48
%S A125961 4,0,6,0,1,5,6,9,3,8,5,5,7,4,0,9,9,5,1,0,7,8,1,7,9,8,5,1,3,3,1,9,0,0,
%T A125961 8,9,7,8,6,5,1,2,9,1,7,8,6,3,6,9,4,5,0,4,9,4,6,0,3,9,0,6,8,4,7,7,2,6,
%U A125961 3,5,0,7,9,7,8,7,7,8,1,3,8,5,3,8,9,7,6,8,6,6,0,1,6,7,1,5,3,9,8,5
%N A125961 Decimal expansion of e * sqrt(Pi) * erf(1).
%H A125961 G. C. Greubel, <a href="/A125961/b125961.txt">Table of n, a(n) for n = 1..5000</a>
%H A125961 J.-P. Allouche and T. Baruchel, <a href="http://arxiv.org/abs/1408.2206">Variations on an error sum function for the convergents of some powers of e</a>, arXiv preprint arXiv:1408.2206 [math.NT], 2014.
%F A125961 Equals Sum_{k >= 1} (2^k / (2k-1)!!).
%F A125961 Equals Integral_{x=0..1} e^x dx/sqrt(1-x). - _Amiram Eldar_, Jul 04 2020
%e A125961 c = 4.06015693855740995107817985133190089786512917863694504946039...
%t A125961 RealDigits[N[E Sqrt[Pi] Erf[1], 100]][[1]]
%o A125961 (MATLAB) exp(1)*sqrt(pi)*erf(1) % _Altug Alkan_, Nov 11 2015
%o A125961 (PARI) exp(1)*sqrt(Pi)*(1-erfc(1)) \\ _Michel Marcus_, Nov 11 2015
%o A125961 (PARI) vector(100, n, if(n<1, 0, default(realprecision, n+2); floor((exp(1)*sqrt(Pi)*(1-erfc(1)))*10^(n-1))%10)) \\ _Altug Alkan_, Nov 11 2015
%K A125961 cons,nonn
%O A125961 1,1
%A A125961 _Fredrik Johansson_, Feb 06 2007