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A020765 Decimal expansion of 1/sqrt(8). 13
3, 5, 3, 5, 5, 3, 3, 9, 0, 5, 9, 3, 2, 7, 3, 7, 6, 2, 2, 0, 0, 4, 2, 2, 1, 8, 1, 0, 5, 2, 4, 2, 4, 5, 1, 9, 6, 4, 2, 4, 1, 7, 9, 6, 8, 8, 4, 4, 2, 3, 7, 0, 1, 8, 2, 9, 4, 1, 6, 9, 9, 3, 4, 4, 9, 7, 6, 8, 3, 1, 1, 9, 6, 1, 5, 5, 2, 6, 7, 5, 9, 7, 1, 2, 5, 9, 6, 8, 8, 3, 5, 8, 1, 9, 1, 0, 3, 9, 3 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
Multiplied by 10, this is the real and the imaginary part of sqrt(25i). - Alonso del Arte, Jan 11 2013
Radius of the midsphere (tangent to the edges) in a regular tetrahedron with unit edges. - Stanislav Sykora, Nov 20 2013
The side of the largest cubical present that can be wrapped (with cutting) by a unit square of wrapping paper. See Problem 10716 link. - Michel Marcus, Jul 24 2018
The ratio between the thickness and diameter of a geometrically fair coin having an equal probability, 1/3, of landing on each of its two faces and on its side after being tossed in the air. The calculation is based on comparing the areal projections of the faces and sides of the coin on a circumscribing sphere. (Mosteller, 1965). See A020760 for a physical solution. - Amiram Eldar, Sep 01 2020
REFERENCES
Frederick Mosteller, Fifty challenging problems of probability, Dover, New York, 1965. See problem 38, pp. 10 and 58-60.
LINKS
Michael L. Catalano-Johnson, Daniel Loeb and John Beebee, A cubical gift: Problem 10716, The American Mathematical Monthly, Vol. 108, No. 1 (Jan., 2001), pp. 81-82.
Wikipedia, Tetrahedron.
Wikipedia, Platonic solid.
FORMULA
A010503 divided by 2.
Equals A201488 minus 1/2. Equals 1/(A010487-4) minus 1/4. - Jon E. Schoenfield, Jan 09 2017
EXAMPLE
1/sqrt(8) = 0.353553390593273762200422181052424519642417968844237018294...
MAPLE
Digits:=100; evalf(1/sqrt(8)); # Wesley Ivan Hurt, Mar 27 2014
MATHEMATICA
RealDigits[N[1/Sqrt[8], 200]] (* Vladimir Joseph Stephan Orlovsky, May 27 2010 *)
PROG
(PARI) sqrt(1/8) \\ Charles R Greathouse IV, Apr 25 2016
CROSSREFS
Cf. Midsphere radii in Platonic solids:
A020761 (octahedron),
A010503 (cube),
A019863 (icosahedron),
A239798 (dodecahedron).
Sequence in context: A096634 A105439 A142972 * A112756 A121795 A253027
KEYWORD
nonn,cons
AUTHOR
STATUS
approved

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Last modified March 28 11:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)