A371947 - OEIS

%I #10 Aug 02 2024 12:24:18

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

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

%U 5,5,6,4,4,3,4,4,9,4,8,9,9,3,4,5,2,0

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

%F Equals (18*e^(1/4) + sqrt(Pi)*erfi(1/2))/(16*e^(1/4)).

%F Equals 2*1F1(3;3/2;-1/4) . - _R. J. Mathar_, Aug 02 2024

%e 1.17805454793775278699175529406120869638705368466996...

%t s = Sum[(-1)^k (k + 2)!/(2 k+1)!, {k, 0, Infinity}]

%t d = N[s, 100]

%t First[RealDigits[d]]

%Y Cf. A371942.

%K nonn,cons

%O 1,3

%A _Clark Kimberling_, Apr 28 2024