A371935 Decimal expansion of Sum_{k>=0} (-1)^k / ((k+1)*(2*k+1)!).

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

Offset: 0

Author

Clark Kimberling, Apr 24 2024

Keywords

• nonn
• cons

Examples

			0.91939538826372056519812678511404679253...
		

Crossrefs

Cf. A049470, A243596, A272795, A371936.

Programs

Mathematica

s = N[Sum[(-1)^k/((k + 1) (2 k + 1)!), {k, 0, Infinity}], 120]
First[RealDigits[s]]

PARI

2*(1 - cos(1)) \\ Stefano Spezia, Apr 21 2025

Formula

Equals 2*(1 - cos(1)) = 2 * A371936.

From Hugo Pfoertner, Apr 26 2024: (Start)

Equals A243596/Pi.

Equals A272795^2. (End)