A232812 Decimal expansion of the surface index of a regular tetrahedron.

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

Offset

1,1

Comments

Equivalently, the surface area of a regular octahedron with unit volume. Among Platonic solids, surface indices decrease with increasing number of faces: this one, 6.0 (cube = hexahedron), A232811 (octahedron), A232810 (dodecahedron), and A232809 (icosahedron).

Links

Stanislav Sykora, Table of n, a(n) for n = 1..1000

Wikipedia, Platonic solid.

Index entries for algebraic numbers, degree 6

Formula

Equals 2*sqrt(3)*3^(2/3).

Equals A002194/A020829^(2/3).

Example

7.20562173105601636005279232409725707779044450935589335...

Mathematica

RealDigits[2*Sqrt[3]*3^(2/3), 10, 120][[1]] (* Amiram Eldar, May 25 2023 *)

Prog

(PARI) sqrtn(139968, 6) \\ Charles R Greathouse IV, Apr 25 2016

Crossrefs

Cf. A002194, A020829, A232808 (surface index of a sphere), A232809, A232810, A232811.

Sequence in context: A220674 A102771 A341798 * A245740 A318922 A236565

Adjacent sequences: A232809 A232810 A232811 * A232813 A232814 A232815

Keyword

nonn,cons,easy

Author

Stanislav Sykora, Dec 01 2013

Status

approved