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A232808 Decimal expansion of the surface area of a 3D sphere with unit volume. 10
4, 8, 3, 5, 9, 7, 5, 8, 6, 2, 0, 4, 9, 4, 0, 8, 9, 2, 2, 1, 5, 0, 9, 0, 0, 5, 3, 9, 9, 1, 7, 8, 5, 4, 8, 1, 6, 8, 3, 3, 8, 4, 2, 2, 1, 6, 9, 7, 1, 5, 8, 4, 6, 6, 7, 0, 7, 6, 8, 7, 6, 2, 2, 6, 1, 3, 6, 8, 5, 2, 8, 9, 5, 1, 7, 1, 4, 3, 5, 8, 2, 2, 7, 3, 8, 4, 6 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

More generally, the ratio (surface)/(volume)^(2/3), characteristic of the shape of a bounded 3D body, which is invariant under linear scaling and known as the surface index. Its common value for all spheres is the smallest possible among all closed 3D bodies (for a cube, for example, it is exactly 6.0).

LINKS

Stanislav Sykora, Table of n, a(n) for n = 1..2000

FORMULA

(36*Pi)^(1/3) = 6*A019673^(1/3).

EXAMPLE

4.83597586204940892215090053991785481683384221697158466707687622613685...

MATHEMATICA

RealDigits[(36 Pi)^(1/3), 10, 90][[1]] (* Bruno Berselli, Dec 01 2013 *)

CROSSREFS

Cf. A000796 (Pi), A019673 (Pi/6); other sphere metrics: A019694, A019699, A087198, A087199.

Sequence in context: A204993 A234001 A248946 * A248508 A065191 A229988

Adjacent sequences:  A232805 A232806 A232807 * A232809 A232810 A232811

KEYWORD

nonn,cons,easy

AUTHOR

Stanislav Sykora, Nov 30 2013

STATUS

approved

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Last modified July 20 22:51 EDT 2017. Contains 289629 sequences.