A371940 - OEIS

%I #9 Aug 02 2024 12:18:31

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

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

%U 0,7,0,9,0,7,1,4,5,4,3,6,5,7,6,7,9,7

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

%F Equals (30 e^(1/4) - 41 sqrt(Pi) erfi(1/21))/(32 e^(1/4)).

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

%e -0.1501182327239321333309835282547782759346005...

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

%t d = N[s, 100]

%t First[RealDigits[d]]

%Y Cf. A371938.

%K nonn,cons

%O 0,2

%A _Clark Kimberling_, Apr 27 2024