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A371939
Decimal expansion of Sum_{k>=0} (-1)^k (k+1)! / (2k)!.
1
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
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
KEYWORD
nonn,cons
AUTHOR
Clark Kimberling, Apr 27 2024
STATUS
approved