The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A179294 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A179294

Decimal expansion of radius of inscribed sphere about a regular icosahedron with edge = 1.
(history; published version)

#34 by Charles R Greathouse IV at Sun Feb 16 08:33:12 EST 2025

LINKS

MathWorld, <a href="httphttps://mathworld.wolfram.com/Icosahedron.html">Icosahedron</a>.

Discussion

Sun Feb 16

08:33

OEIS Server: https://oeis.org/edit/global/3014

#33 by Michael De Vlieger at Mon Jan 27 21:13:32 EST 2025

STATUS

proposed

approved

#32 by Stefano Spezia at Mon Jan 27 15:45:40 EST 2025

STATUS

editing

proposed

#31 by Stefano Spezia at Mon Jan 27 15:41:16 EST 2025

MATHEMATICA

RealDigits[N[(Sqrt[42+18Sqrt[5]]/12), 10, 175][[1]]

#30 by Stefano Spezia at Mon Jan 27 15:32:12 EST 2025

PROG

(PARI) sqrt((7+3*sqrt(5))/6)/2 \\ Stefano Spezia, Jan 27 2025

#29 by Stefano Spezia at Mon Jan 27 15:30:37 EST 2025

REFERENCES

Jan Gullberg, Mathematics from the Birth of Numbers, W. W. Norton & Co., NY & London, 1997, §12.4 Theorems and Formulas (Solid Geometry), p. 451.

LINKS

Dr. Math, <a href="http://mathforum.org/dr.math/faq/formulas/faq.polyhedron.html#icosahedron">Icosahedron</a>.

Wikipedia, <a href="http://en.wikipedia.org/wiki/Icosahedron">Icosahedron</a>.

MathWorld, <a href="http://mathworld.wolfram.com/Icosahedron.html">Icosahedron</a>.

<a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a>.

FORMULA

SqrtEquals sqrt(42 + 18*sqrt(5))/12.

MATHEMATICA

a=1; RealDigits[N[(Sqrt[42+18Sqrt[5]]/12)*a, , 175]]

STATUS

approved

editing

#28 by Charles R Greathouse IV at Mon Aug 14 10:32:31 EDT 2023

STATUS

editing

approved

#27 by Charles R Greathouse IV at Mon Aug 14 10:32:29 EDT 2023

LINKS

<a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a>

STATUS

approved

editing

#26 by Jon E. Schoenfield at Wed Jan 19 21:27:07 EST 2022

STATUS

proposed

approved

#25 by Jon E. Schoenfield at Wed Jan 19 21:20:24 EST 2022

STATUS

editing

proposed