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A019881 Decimal expansion of sine of 72 degrees. 18
9, 5, 1, 0, 5, 6, 5, 1, 6, 2, 9, 5, 1, 5, 3, 5, 7, 2, 1, 1, 6, 4, 3, 9, 3, 3, 3, 3, 7, 9, 3, 8, 2, 1, 4, 3, 4, 0, 5, 6, 9, 8, 6, 3, 4, 1, 2, 5, 7, 5, 0, 2, 2, 2, 4, 4, 7, 3, 0, 5, 6, 4, 4, 4, 3, 0, 1, 5, 3, 1, 7, 0, 0, 8, 5, 1, 9, 3, 5, 0, 1, 7, 1, 8, 7, 9, 2, 8, 1, 0, 9, 7, 0, 8, 1, 1, 3, 8, 1 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Circumradius of pentagonal pyramid (Johnson solid 2) with edge 1. - Vladimir Joseph Stephan Orlovsky, Jul 19 2010

Circumscribed sphere radius for a regular icosahedron with unit edges. - Stanislav Sykora, Feb 10 2014

LINKS

Table of n, a(n) for n=0..98.

Wikipedia, Exact trigonometric constants

Wikipedia, Platonic solid

Wolfram Alpha, Johnson solid 2

FORMULA

Equals sqrt((5+sqrt(5))/8) = cos(Pi/10). - Zak Seidov, Nov 18 2006

Equals 2F1(13/20,7/20;1/2;3/4) / 2. - R. J. Mathar, Oct 27 2008

Equals the real part of i^(1/5). - Stanislav Sykora, Apr 25 2012

Equals A001622*A182007/2. - Stanislav Sykora, Feb 10 2014

EXAMPLE

0.95105651629515357211643933337938214340569863412575022244730564443...

MATHEMATICA

RealDigits[Sqrt[(5 + Sqrt[5])/8], 10, 111]  (* Robert G. Wilson v *)

CROSSREFS

Cf. A001622, A102208, A179290, A179292, A179294, A179449, A179450, A179451, A179452, A179552, A179553, A182007.

Cf. Platonic solids circumradii: A010503 (octahedron), A010527 (cube), A179296 (dodecahedron), A187110 (tetrahedron). - Stanislav Sykora, Feb 10 2014

Sequence in context: A197378 A232738 A201395 * A049256 A019982 A198421

Adjacent sequences:  A019878 A019879 A019880 * A019882 A019883 A019884

KEYWORD

nonn,cons

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified April 24 01:06 EDT 2014. Contains 240947 sequences.