A371939 Decimal expansion of Sum_{k>=0} (-1)^k (k+1)! / (2k)!.

2, 1, 9, 4, 5, 4, 5, 2, 0, 6, 2, 2, 4, 7, 2, 1, 3, 0, 0, 8, 2, 4, 4, 7, 0, 5, 9, 3, 8, 7, 9, 1, 3, 0, 3, 6, 1, 2, 9, 4, 6, 3, 1, 5, 3, 3, 0, 0, 3, 8, 4, 9, 5, 2, 3, 1, 0, 8, 2, 5, 3, 7, 9, 2, 0, 8, 4, 4, 3, 5, 5, 6, 5, 5, 0, 5, 1, 0, 0, 6, 5, 4, 7, 9, 0, 3

Offset

0,1

Links

Table of n, a(n) for n=0..85.

Formula

Equals (6 e^(1/4) - 5 Sqrt(Pi) erfi(1/2))/(8 e^(1/4)).

Equals 1F1(2;1/2;-1/4). - R. J. Mathar, Aug 27 2024

Example

0.219454520622472130082447059387913036129463153300...

Mathematica

s = Sum[(-1)^k (k + 1)!/(2 k)!, {k, 0, Infinity}]
d = N[s, 100]
First[RealDigits[d]]

Crossrefs

Cf. A371937.

Sequence in context: A166890 A197411 A124905 * A293417 A295737 A021086

Adjacent sequences: A371936 A371937 A371938 * A371940 A371941 A371942

Keyword

nonn,cons

Author

Clark Kimberling, Apr 27 2024

Status

approved