A232808 Decimal expansion of the surface area of a 3D sphere with unit volume.

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

Offset: 1

Author

Stanislav Sykora, Nov 30 2013

Keywords

• nonn
• cons
• easy

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).

Examples

			4.83597586204940892215090053991785481683384221697158466707687622613685...
		

Links

• Stanislav Sykora, Table of n, a(n) for n = 1..2000
• Index entries for transcendental numbers

Crossrefs

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

Programs

Mathematica

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

Formula

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