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 A371946 #13 Aug 02 2024 12:26:23
%S A371946 7,1,2,2,1,8,1,9,1,7,5,1,0,1,1,1,4,7,9,6,7,0,2,1,1,7,6,2,4,4,8,3,4,7,
%T A371946 8,5,5,4,8,2,1,4,7,3,8,6,7,9,8,4,6,0,1,9,0,7,5,6,6,9,8,4,8,3,1,6,6,2,
%U A371946 2,5,7,7,3,7,9,7,9,5,9,7,3,8,0,8,3,8
%N A371946 Decimal expansion of Sum_{k>=0} (-1)^k * (k+1)! / (2k+1)!.
%F A371946 Equals (2*e^(1/4) + sqrt(Pi)*erfi(1/2))/(4*e^(1/4)).
%F A371946 Equals 1F1(2;3/2;-1/4) . - _R. J. Mathar_, Aug 02 2024
%e A371946 0.712218191751011147967021176244834785548214...
%t A371946 s = Sum[(-1)^k (k + 1)!/(2 k+1)!, {k, 0, Infinity}]
%t A371946 d = N[s, 100]
%t A371946 First[RealDigits[d]]
%Y A371946 Cf. A371941.
%K A371946 nonn,cons
%O A371946 0,1
%A A371946 _Clark Kimberling_, Apr 28 2024