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 A086089 Decimal expansion of 3*sqrt(3)/(2*Pi). 3
 8, 2, 6, 9, 9, 3, 3, 4, 3, 1, 3, 2, 6, 8, 8, 0, 7, 4, 2, 6, 6, 9, 8, 9, 7, 4, 7, 4, 6, 9, 4, 5, 4, 1, 6, 2, 0, 9, 6, 0, 7, 9, 7, 2, 0, 5, 4, 9, 9, 6, 0, 9, 7, 9, 1, 9, 9, 0, 4, 9, 0, 3, 0, 4, 3, 6, 5, 4, 5, 4, 5, 5, 2, 0, 3, 9, 0, 4, 6, 9, 2, 2, 6, 0, 5, 7, 0, 0, 4, 3, 2, 3, 4, 7, 5, 6, 3, 3, 3, 8, 1, 1 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Limiting ratio of areas in the disk-covering problem. From Daniel Forgues, May 26 2010: (Start) Consider: A060544, Centered 9-gonal (or nonagonal) numbers, starting with a(1)=1, P_c(9, n), n >= 1. Every third triangular number, starting with a(1)=1, P(3, 3n-2), n >= 1. Then: 1/(sum_{n=0..infinity} 1/binomial(3n+2,2)) = 1/(sum_{n=1..infinity} 1/binomial(3n-1,2)) = 1/(sum_{n=1..infinity} 1/P_c(9,n)) = 1/(sum_{n=1..infinity} 1/P(3,3n-2)) = 1/(sum_{n=1..infinity} 1/A060544(n)) = this constant. (End) Also, decimal expansion of product_{n>=1} (1 - 1/(3n)^2). [Bruno Berselli, Apr 02 2013] REFERENCES S. R. Finch, Mathematical Constants, Cambridge, 2003, Sections 5.9 p. 325 and 8.2 p. 486. LINKS FORMULA Equals sinc(Pi/3). - Peter Luschny, Oct 04 2019 EXAMPLE 0.8269933431326880742669897474694541620960797205499609791990... MATHEMATICA RealDigits[3 Sqrt[3]/(2 Pi), 10, 110][[1]] (* or, from the third comment: *) RealDigits[N[Product[1 - 1/(3 n)^2, {n, 1, Infinity}], 110]][[1]] (* Bruno Berselli, Apr 02 2013 *) CROSSREFS Cf. A060544. Sequence in context: A120219 A240976 A199158 * A091350 A099876 A153203 Adjacent sequences:  A086086 A086087 A086088 * A086090 A086091 A086092 KEYWORD nonn,cons,easy AUTHOR Eric W. Weisstein, Jul 08 2003 STATUS approved

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Last modified October 21 22:47 EDT 2019. Contains 328315 sequences. (Running on oeis4.)