cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A193887 Decimal expansion of Pi * sqrt(2)/8.

Original entry on oeis.org

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

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Author

Alonso del Arte, Aug 07 2011

Keywords

Comments

This number arises as an addend in one way of giving the closed form of sum(k>=0, (-1)^k/(4*k + 1) ), for example, in Spiegel et al. (2009).

Examples

			0.55536036726979578088...
		

References

  • Murray R. Spiegel, Seymour Lipschutz, John Liu. Mathematical Handbook of Formulas and Tables, 3rd Ed. Schaum's Outline Series. New York: McGraw-Hill (2009): p. 135, equation 21.17

Crossrefs

Programs

  • Magma
    R:= RealField(); Pi(R)*Sqrt(2)/8; // G. C. Greubel, Feb 02 2018
  • Mathematica
    RealDigits[(Pi Sqrt[2])/8, 10, 100][[1]]
  • PARI
    Pi*sqrt(2)/8 \\ G. C. Greubel, Feb 02 2018
    

Formula

Equals Pi/(4*sqrt(2)).
Equals Sum_{k >= 0} (-1)^k * (4*k + 2)/((4*k + 1)*(4*k + 3)). - Peter Bala, Sep 21 2016
From Amiram Eldar, Aug 15 2020: (Start)
Equals Integral_{x=0..oo} 1/(x^2 + 8) dx.
Equals Integral_{x=0..oo} 1/(8*x^2 + 1) dx.
Equals Integral_{x=0..oo} 1/(1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + x^7) dx. (End)