OFFSET
1,2
COMMENTS
Coordinate of a control point for a degree-5 integration formula for 7 points over the unit circle. [Stroud & Secrest]
Also real and imaginary part of sqrt(-3i). - Alonso del Arte, Dec 11 2012
Area of the quadrilateral obtained when slicing a unit cube with a plane passing through opposite vertices and the middle of opposite edges. See CNRS link. - Michel Marcus, Mar 26 2016
LINKS
Daniel Starodubtsev, Table of n, a(n) for n = 1..10000
Ana Rechtman, Mars 2016, 3e défi, Images des Mathématiques, CNRS, 2016.
A. H. Stroud, D. Secrest, Approximate integration formulas for certain spherically symmetric regions, Math. Comp. 17 (82) (1963) 105.
FORMULA
Equals 2*A187110.
Equals Sum_{k>=0} binomial(1/2, k)/2^k. - Bruno Berselli, Sep 11 2015
From Amiram Eldar, Aug 02 2020: (Start)
Equals Product_{k>=0} (1 + (-1)^k/(6*k + 3)).
Equals Sum_{k>=0} binomial(2*k,k)/12^k.
Equals 1 + Sum_{k>=1} (2*k - 1)!!/((2*k)!! * 3^k). (End)
Equals A010464/2. - R. J. Mathar, Feb 23 2021
EXAMPLE
1.2247448713915890490986420373529456959829737403283350642163...
MATHEMATICA
RealDigits[Sqrt[3/2], 10, 105][[1]] (* Alonso del Arte, Dec 11 2012 *)
CROSSREFS
KEYWORD
AUTHOR
Eric Desbiaux, Jul 30 2008
STATUS
approved