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%I #45 Jul 29 2020 20:35:58
%S 4,1,8,8,7,9,0,2,0,4,7,8,6,3,9,0,9,8,4,6,1,6,8,5,7,8,4,4,3,7,2,6,7,0,
%T 5,1,2,2,6,2,8,9,2,5,3,2,5,0,0,1,4,1,0,9,4,6,3,3,2,5,9,4,5,6,4,1,0,4,
%U 2,1,8,7,5,0,4,8,2,7,8,6,6,4,8,3,7,3,7,9,7,6,7,1,2,2,8,2,2,7,5
%N Decimal expansion of 2*Pi/15 = (4*Pi/3)/10.
%C With offset 1, decimal expansion of 4*Pi/3, the volume of a sphere of radius 1. - _Omar E. Pol_, Aug 27 2007, Sep 25 2013
%C 2*Pi/15 is the common value of the base angles of the isosceles triangle formed at the common vertex of the figure obtained by gluing a hexagon and a pentagon, both regular, along a common side, as shown in the CNRS link. - _Michel Marcus_, Mar 06 2015
%C This is also the surface area (in some cubic length unit (l.u.)) of a sphere with a central cylinder symmetrical hole of length 2 l.u. Thanks to Sven Heinemeyer for reminding me of this classical astonishing result. See e.g., Bild der Wissenschaft, Januar 1964, p. 75, or the Gardner reference, Problem 7 on p. 51. In two dimensions things are different. See A258146. - _Wolfdieter Lang_, May 31 2015
%D Bild der Wissenschaft, Januar 1964.
%D Martin Gardner, Mathematische Rätsel und Probleme, 3. Auflage, Friedr. Vieweg + Sohn, Braunschweig, 1975, p. 51 (in German). In English: Mathematical Puzzles and Diversions from "Scientific American", Simon and Schuster, N. Y. 1959/1961.
%H Ivan Panchenko, <a href="/A019699/b019699.txt">Table of n, a(n) for n = 0..1000</a>
%H Ana Rechtman, <a href="http://images.math.cnrs.fr/Fevrier-2015-4eme-defi.html">Février 2015, 4ème défi</a>, Images des Mathématiques, CNRS, 2015.
%H <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F (1/10)*volume of the unit sphere in R^3 = (1/10)*Pi^(3/2)/gamma(1+3/2). - _Benoit Cloitre_, Jun 19 2003
%e 2*Pi/15 = 0.418879020478639098461685784437267...
%e 4*Pi/3 = 4.18879020478639098461685784437267... - _Omar E. Pol_, Sep 25 2013
%t RealDigits[(2 Pi)/15,10,120][[1]] (* _Harvey P. Dale_, Mar 22 2015 *)
%o (PARI) 2*Pi/15 \\ _Charles R Greathouse IV_, Jan 09 2018
%Y Cf. A000796, A019692, A019693.
%K nonn,cons
%O 0,1
%A _N. J. A. Sloane_
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