

A002580


Decimal expansion of cube root of 2.
(Formerly M1354 N0521)


35



1, 2, 5, 9, 9, 2, 1, 0, 4, 9, 8, 9, 4, 8, 7, 3, 1, 6, 4, 7, 6, 7, 2, 1, 0, 6, 0, 7, 2, 7, 8, 2, 2, 8, 3, 5, 0, 5, 7, 0, 2, 5, 1, 4, 6, 4, 7, 0, 1, 5, 0, 7, 9, 8, 0, 0, 8, 1, 9, 7, 5, 1, 1, 2, 1, 5, 5, 2, 9, 9, 6, 7, 6, 5, 1, 3, 9, 5, 9, 4, 8, 3, 7, 2, 9, 3, 9, 6, 5, 6, 2, 4, 3, 6, 2, 5, 5, 0, 9, 4, 1, 5, 4, 3, 1, 0, 2, 5
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OFFSET

1,2


COMMENTS

For doubling the cube using origami and a standard geometric construction employing two right angles see the W. Lang link, Application 2, p. 14, and the references given there. See also the L. Newton link.  Wolfdieter Lang, Sep 02 2014
Length of an edge of a cube with volume 2.  Jared Kish, Oct 16 2014
For any positive real c, the mappings R(x)=(c*x)^(1/4) and S(x)=sqrt(c/x) have the same unique attractor c^(1/3), to which their iterated applications converge from any complex plane point. The present case is obtained setting c=2. It is noteworthy that in this way one can evaluate cube roots using only square roots. The CROSSREFS list some other cases of cube roots to which this comment might apply.  Stanislav Sykora, Nov 11 2015
The cube root of any positive number can be connected to the Philo lines (or Philon lines) for a 90degree angle. If the equation x^32 is represented using Lill's method, it can be shown that the path of the root 2^(1/3) creates the shortest segment (Philo line) from the x axis through (1,2) to the y axis. For more details see the article "Lill's method and the Philo Line for Right Angles" linked below.  Raul Prisacariu, Apr 06 2024


REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Horace S. Uhler, Manyfigure approximations for cubed root of 2, cubed root of 3, cubed root of 4, and cubed root of 9 with chi2 data. Scripta Math. 18, (1952). 173176.


LINKS



FORMULA

(2^(1/3)  2^(1/3) * sqrt(3))^3 = (2^(1/3) + 2^(1/3) * sqrt(3))^3 = 16.  Alonso del Arte, Jan 04 2015
Set c=2 in the identities c^(1/3) = sqrt(c/sqrt(c/sqrt(c/...))) = sqrt(sqrt(c*sqrt(sqrt(c*sqrt(sqrt(...)))))).  Stanislav Sykora, Nov 11 2015
Equals Product_{k>=0} (1 + (1)^k/(3*k + 2)).  Amiram Eldar, Jul 25 2020
Equals Sum_{n >= 0} (1/(3*n+1)  1/(3*n2))*binomial(1/3,n) = (3/2)* hypergeom([1/3, 2/3], [4/3], 1). Cf. A290570.
Equals 4/3  4*Sum_{n >= 1} binomial(1/3,2*n+1)/(6*n1) = (4/3)*hypergeom ([1/2, 1/6], [3/2], 1).
Equals hypergeom([2/3, 1/6], [1/2], 1).
Equals hypergeom([2/3, 1/6], [4/3], 1). (End)


EXAMPLE

1.2599210498948731647672106072782283505702514...


MAPLE



MATHEMATICA



PROG

(PARI) default(realprecision, 20080); x=2^(1/3); for (n=1, 20000, d=floor(x); x=(xd)*10; write("b002580.txt", n, " ", d)); \\ Harry J. Smith, May 07 2009
(PARI) default(realprecision, 100); x= 2^(1/3); for(n=1, 100, d=floor(x); x=(xd)*10; print1(d, ", ")) \\ Altug Alkan, Nov 14 2015


CROSSREFS



KEYWORD



AUTHOR



STATUS

approved



