A334632 Decimal expansion of Sum_{k>=0} (-1)^k / ((2*k)!)^2.

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

Offset

0,1

Links

Table of n, a(n) for n=0..105.

Eric Weisstein's World of Mathematics, Kelvin Functions.

Wikipedia, Kelvin functions.

Formula

Equals Re(BesselJ(0, 2*exp(3*Pi*i/4))).

Example

0.75173418271380822855099890123074657595958657660729200273884...

Maple

evalf(Sum((-1)^k/(2*k)!^2, k=0..infinity), 120);

Mathematica

RealDigits[KelvinBer[0, 2], 10, 120][[1]]
RealDigits[Re[Hypergeometric0F1Regularized[1, I]], 10, 120][[1]]
RealDigits[HypergeometricPFQ[{}, {1/2, 1/2, 1}, -1/16], 10, 120][[1]] (* Vaclav Kotesovec, Jul 19 2021 *)

Prog

(PARI) sumalt(k=0, (-1)^k/(2*k)!^2)

Crossrefs

Cf. A334379.

Sequence in context: A233090 A254177 A021575 * A154870 A098687 A021137

Adjacent sequences: A334629 A334630 A334631 * A334633 A334634 A334635

Keyword

nonn,cons

Author

Vaclav Kotesovec, Sep 10 2020

Status

approved