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 A020761 Decimal expansion of 1/2. 12
 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Real part of all nontrivial zeros of the Riemann zeta function (assuming the Riemann hypothesis to be true). - Alonso del Arte, Jul 02 2011 Radius of a sphere with surface area Pi. - Omar E. Pol, Aug 09 2012 Radius of the midsphere (tangent to the edges) in a regular octahedron with unit edges. Also radius of the inscribed sphere (tangent to faces) in a cube with unit edges. - Stanislav Sykora, Mar 27 2014 Construct a rectangle of maximal area inside an arbitrary triangle. The ratio of the rectangle's area to the triangle's area is 1/2. - Rick L. Shepherd, Jul 30 2014 LINKS Wikipedia, Riemann zeta function Wikipedia, Platonic solid Index entries for linear recurrences with constant coefficients, signature (1). FORMULA Sum(k=1,2,3...)(1/3^k). Hence 1/2 = 0.1111111111111... in base 3. Cosine of 60 degrees, i.e., cos(Pi/3). -zeta(0), zeta being the Riemann function. - Stanislav Sykora, Mar 27 2014 a(0) = 5; a(n) = 0, n > 0. - Wesley Ivan Hurt, Mar 27 2014 a(n) = 5 * floor(1/(n + 1)). - Wesley Ivan Hurt, Mar 27 2014 EXAMPLE 1/2 = 0.50000000000000... MAPLE Digits:=100; evalf(1/2); # Wesley Ivan Hurt, Mar 27 2014 MATHEMATICA RealDigits[1/2, 10, 128][[1]] (* Alonso del Arte, Dec 13 2013 *) LinearRecurrence[{1}, {5, 0}, 99] (* Ray Chandler, Jul 15 2015 *) PROG (PARI) { default(realprecision); x=1/2*10; for(n=1, 100, d=floor(x); x=(x-d)*10; print1(d, ", ")) } \\ Felix FrÃ¶hlich, Jul 24 2014 (PARI) a(n) = 5*(n==0); \\ Michel Marcus, Jul 25 2014 CROSSREFS Cf. In platonic solids: midsphere radii: A020765 (tetrahedron), A010503 (cube), A019863 (icosahedron), A239798 (dodecahedron); insphere radii: A020781 (tetrahedron), A020763 (octahedron), A179294 (icosahedron), A237603 (dodecahedron). Sequence in context: A115544 A241471 A152623 * A281462 A236239 A047752 Adjacent sequences:  A020758 A020759 A020760 * A020762 A020763 A020764 KEYWORD nonn,cons,easy AUTHOR STATUS approved

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Last modified January 17 19:58 EST 2019. Contains 319251 sequences. (Running on oeis4.)