A247719 Decimal expansion of Integral_{t=0..Pi/2} sqrt(tan(t)) dt.

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

Offset

1,1

Links

G. C. Greubel, Table of n, a(n) for n = 1..10000

D. H. Bailey and J. M. Borwein, Highly Parallel, High-Precision Numerical Integration p. 7. (2005) Lawrence Berkeley National Laboratory.

Philippe Flajolet and Robert Sedgewick, Analytic Combinatorics, Cambridge Univ. Press, 2009, pp. 235-236.

Formula

Equals Pi/sqrt(2).

Equals A063448/2.

c = 2*( Sum_{k >= 0} (-1)^k/(4*k + 1) + Sum_{k >= 0} (-1)^k/(4*k + 3) ) = 2*(A181048 + A181049). - Peter Bala, Sep 21 2016

From Amiram Eldar, Aug 07 2020: (Start)

Equals Integral_{x=0..Pi} 1/(cos(x)^2 + 1) dx = Integral_{x=0..Pi} 1/(sin(x)^2 + 1) dx.

Equals Integral_{x=-oo..oo} 1/(x^4 + 1) dx.

Equals Integral_{x=-oo..oo} x^2/(x^4 + 1) dx.

Equals Integral_{x=0..oo} log(1 + 1/(2 * x^2)) dx. (End)

Equals Integral_{x=0..2*Pi} 1/(3 + sin(x)) dx; since for a>1: Integral_{x=0..2*Pi} 1/(a + sin(x)) dx = 2*Pi/sqrt(a^2-1). - Bernard Schott, Feb 19 2023

Equals 20/9 - 160*Sum_{n >= 1} 1/((64*n^2 - 1)*(64*n^2 - 4)*(64*n^2 - 9)). - Peter Bala, Nov 09 2023

Example

2.22144146907918312350794049503034684930731...

Mathematica

RealDigits[Pi/Sqrt[2], 10, 104] // First

Prog

(PARI) default(realprecision, 100); Pi/sqrt(2) \\ G. C. Greubel, Sep 07 2018
(Magma) SetDefaultRealField(RealField(100)); R:= RealField(); Pi(R)/Sqrt(2); // G. C. Greubel, Sep 07 2018

Crossrefs

Cf. A063448, A093954, A193887, A244976, A181048, A181049, A186706.

Sequence in context: A105777 A014572 A071458 * A131308 A261360 A372014

Adjacent sequences: A247716 A247717 A247718 * A247720 A247721 A247722

Keyword

nonn,cons,easy

Author

Jean-François Alcover, Sep 23 2014

Status

approved