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A285871 Decimal expansion of 1/sqrt(2 - sqrt(2)) (reciprocal of A101464). 1
1, 3, 0, 6, 5, 6, 2, 9, 6, 4, 8, 7, 6, 3, 7, 6, 5, 2, 7, 8, 5, 6, 6, 4, 3, 1, 7, 3, 4, 2, 7, 1, 8, 7, 1, 5, 3, 5, 8, 3, 7, 6, 1, 1, 8, 8, 3, 4, 9, 2, 6, 9, 5, 2, 7, 5, 4, 8, 8, 9, 8, 3, 6, 6, 9, 0, 8, 0, 8, 1, 0, 4, 1, 4, 6, 1, 1, 9, 2, 0, 5, 0, 9, 5, 1, 8, 5, 3, 7, 2, 0, 1, 9, 2, 6, 2, 8, 1, 4 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

This number is the length ratio of the radius of a circle and the side of the inscribed octagon.

In the Corbalán reference, pp. 61-62, this number is called Cordoba number or Cordoba proportion, attributed to the architect Rafael de la Hoz (1924-2000) who used the rectangle with this proportion to explain the structure of the Mihrab of Cordoba.

REFERENCES

Fernando Corbalán, Der goldene Schnitt, Librero, 2017. Original: La proportión áurea, RBA Contenidos Editoriales y Audiovisuales S. A. U., 2010. English: The golden Ratio, 2012, RBA Coleccionables.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..10000

Eric Weisstein's World of Mathematics, Octagon.

Wikipedia, Octagon.

FORMULA

Equals 1/(2*sin(Pi/8)) = 1/A101464.

EXAMPLE

0.130656296487637652785664317342718715358376118834926952754889836690808104146...

MAPLE

evalf((sqrt(2-sqrt(2)))^(-1), 100); # Muniru A Asiru, Oct 11 2018

MATHEMATICA

RealDigits[1/Sqrt[2 - Sqrt[2]], 10, 100][[1]] (* Indranil Ghosh, May 11 2017 *)

PROG

(Python)

from sympy import N, sqrt

print N(1/sqrt(2 - sqrt(2)), 100) # Indranil Ghosh, May 11 2017

(PARI) default(realprecision, 100); 1/sqrt(2 - sqrt(2)) \\ G. C. Greubel, Oct 10 2018

(MAGMA) SetDefaultRealField(RealField(100)); 1/Sqrt(2 - Sqrt(2)); // G. C. Greubel, Oct 10 2018

CROSSREFS

Cf. A101464, A179260.

Sequence in context: A109693 A188858 A199610 * A004606 A019808 A182145

Adjacent sequences:  A285868 A285869 A285870 * A285872 A285873 A285874

KEYWORD

nonn,cons,easy

AUTHOR

Wolfdieter Lang, May 11 2017

STATUS

approved

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Last modified January 17 18:48 EST 2019. Contains 319251 sequences. (Running on oeis4.)