A384142 Decimal expansion of the volume of a gyroelongated square bipyramid with unit edge.

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

Offset

1,2

Comments

The gyroelongated square bipyramid is Johnson solid J_17.

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Wikipedia, Gyroelongated square bipyramid.

Index entries for algebraic numbers, degree 4.

Formula

Equals (sqrt(2) + sqrt(4 + 3*sqrt(2)))/3 = (A002193 + sqrt(4 + A010474))/3.

Equals the largest real root of 81*x^4 - 108*x^2 - 72*x-14.

Example

1.428404502627748400527146549078867927980904164...

Mathematica

First[RealDigits[(Sqrt[2] + Sqrt[4 + Sqrt[18]])/3, 10, 100]] (* or *)
First[RealDigits[PolyhedronData["J17", "Volume"], 10, 100]]

Crossrefs

Cf. A010502 (surface area).

Cf. A002193, A010474, A179638.

Sequence in context: A026192 A026142 A095399 * A250718 A068504 A382589

Adjacent sequences: A384139 A384140 A384141 * A384143 A384144 A384145

Keyword

nonn,cons,easy

Author

Paolo Xausa, May 22 2025

Status

approved