A232817 Decimal expansion of the open-tube surface index constant.

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

Offset: 1

Author

Stanislav Sykora, Dec 05 2013

Keywords

• nonn
• cons
• easy

Comments

The external surface index of an open-ended cylinder (tube) equals this constant, multiplied by (Length/Diameter)^(1/3).

For a general definition of surface index, see A232808.

Links

• Stanislav Sykora, Table of n, a(n) for n = 1..1000
• Wikipedia, Cylinder (geometry).

Crossrefs

Cf. Other surface indices: A232808 (spheres), A232809, A232810, A232811, A232812 (platonic solids), A232813 (closed cylinders), A232814 (open cylinders), A232815 (closed cones), A232816 (open cones).

Programs

Mathematica

RealDigits[2 * Surd[2 * Pi, 3], 10, 120][[1]] (* Amiram Eldar, May 17 2023 *)

Formula

Equals (16*Pi)^(1/3) = 2*(2*Pi)^(1/3).