The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A177870 Decimal expansion of 3*Pi/4. 3
 2, 3, 5, 6, 1, 9, 4, 4, 9, 0, 1, 9, 2, 3, 4, 4, 9, 2, 8, 8, 4, 6, 9, 8, 2, 5, 3, 7, 4, 5, 9, 6, 2, 7, 1, 6, 3, 1, 4, 7, 8, 7, 7, 0, 4, 9, 5, 3, 1, 3, 2, 9, 3, 6, 5, 7, 3, 1, 2, 0, 8, 4, 4, 4, 2, 3, 0, 8, 6, 2, 3, 0, 4, 7, 1, 4, 6, 5, 6, 7, 4, 8, 9, 7, 1, 0, 2, 6, 1, 1, 9, 0, 0, 6, 5, 8, 7, 8, 0, 0, 9, 8, 6, 6, 1, 1 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS As radians, this is equal to 135 degrees (on an analog clock, the span of 22 minutes and 30 seconds). - Alonso del Arte, Feb 03 2013 Ratio of the area of an arbelos to the area of its associated parbelos. - Jonathan Sondow, Nov 28 2013 (3*Pi/4)*a^2 is the area between a cissoid of Diocles and its asymptote when polar equation of cissoid is r = a* sin^2(t)/cos(t) and Cartesian equation is x * (x^2+y^2) = a * y^2 or y = +- x * sqrt(x/(a-x)). See the curve at the Mathcurve link and formula. - Bernard Schott, Jul 14 2020 REFERENCES Jonathan Borwein & Peter Borwein, A Dictionary of Real Numbers. Pacific Grove, California: Wadsworth & Brooks/Cole Advanced Books & Software (1990) p. 168 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 Robert Ferréol, Cissoid of Diocles, Mathcurve. J. Sondow, The parbelos, a parabolic analog of the arbelos, arXiv:1210.2279 [math.HO], 2012-2013: Amer. Math. Monthly 120 (2013) 929-935. E. Tsukerman, Solution of Sondow's problem: a synthetic proof of the tangency property of the parbelos, arXiv 2012. FORMULA Equals 0.75*A000796 = 3*A003881 = 6*A019675 = A122952/4. Equals 1 + (3/5) + (3*4)/(5*7) + (3*4*5)/(5*7*9) + ... = hypergeom([3,1],[5/2],1/2). - Peter Bala, Oct 30 2019 Equals 2 * Integral_{x=0..1} x * sqrt(x/(1-x)) dx (cissoid). - Bernard Schott, Jul 14 2020 Equals Sum_{k>=1} arctan(2/k^2). - Amiram Eldar, Aug 10 2020 EXAMPLE 2.35619449019234492884698253745962716314787704953132936573120... MAPLE evalf(3*Pi/4) ; MATHEMATICA RealDigits[N[3(Pi/4), 110]][] CROSSREFS Reciprocal of A232715. Cf. A000796, A003881, A019675, A122952. Sequence in context: A157260 A336017 A291486 * A094872 A201744 A152206 Adjacent sequences:  A177867 A177868 A177869 * A177871 A177872 A177873 KEYWORD nonn,cons,easy AUTHOR R. J. Mathar, Dec 13 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 16 21:55 EDT 2021. Contains 345080 sequences. (Running on oeis4.)