A371936 Decimal expansion of Sum_{k>=0} (-1)^k / (2*(k+1)*(2*k+1)!).

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

Offset: 0

Author

Clark Kimberling, Apr 24 2024

Keywords

• nonn
• cons

Examples

			0.459697694131860282599063392557023396267689579382077772...
		

Crossrefs

Cf. A049470, A206533, A371935.

Programs

Mathematica

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

PARI

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

Formula

Equals 1 - cos(1) = A371935/2 = 1 - A049470.

Equals 1/A206533. - Hugo Pfoertner, Apr 26 2024