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 A244854 Decimal expansion of Pi^2/32. 7
 3, 0, 8, 4, 2, 5, 1, 3, 7, 5, 3, 4, 0, 4, 2, 4, 5, 6, 8, 3, 8, 5, 7, 7, 8, 4, 3, 7, 4, 6, 1, 2, 9, 7, 2, 2, 9, 7, 8, 5, 5, 3, 1, 0, 6, 4, 7, 6, 2, 7, 4, 7, 0, 7, 0, 7, 5, 4, 1, 7, 1, 6, 8, 0, 0, 6, 8, 7, 6, 4, 0, 0, 7, 0, 0, 6, 0, 0, 1, 6, 3, 8, 4, 3, 8, 0, 5 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Probability that a point selected uniformly at random from the unit 4-cube is in the unit 4-sphere. Let S(n) = 1 - 1/3 + 1/5 - ... + ((-1)^(n-1))/(2n-1). Then Sum{n >=1} ((-1)^(n-1))*S(n) /(2n+1) = Pi^2 /32. The convergence is very slow. - Michel Lagneau, Feb 27 2015 LINKS FORMULA Equals Integral_{0..infinity} x^2*BesselK(0, x)^2 dx. - Jean-François Alcover, Apr 15 2015 Equals Integral_{x=0..1} arctan(x)/(1+x^2) dx. - Amiram Eldar, Aug 09 2020 EXAMPLE Choose -1 <= w, x, y, z <= 1 uniformly at random. Then this constant is the probability that w^2 + x^2 + y^2 + z^2 <= 1. MAPLE Digits:=100; evalf(Pi^2/32); # Wesley Ivan Hurt, Feb 27 2015 MATHEMATICA RealDigits[Pi^2/32, 10, 120][[1]] (* Harvey P. Dale, Jul 13 2014 *) PROG (PARI) Pi^2/32 CROSSREFS Cf. A003881 (2-dimensional analog), A019673 (3-dimensional analog). Sequence in context: A317300 A007391 A247668 * A144807 A157957 A201577 Adjacent sequences:  A244851 A244852 A244853 * A244855 A244856 A244857 KEYWORD nonn,cons AUTHOR Charles R Greathouse IV, Jul 07 2014 STATUS approved

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Last modified May 14 19:38 EDT 2021. Contains 343902 sequences. (Running on oeis4.)