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

Author

Paolo Xausa, May 22 2025

Keywords

• nonn
• cons
• easy

Comments

The gyroelongated square bipyramid is Johnson solid J_17.

Examples

			1.428404502627748400527146549078867927980904164...
		

Links

• Paolo Xausa, Table of n, a(n) for n = 1..10000
• Wikipedia, Gyroelongated square bipyramid.

Crossrefs

Cf. A010502 (surface area).

Cf. A002193, A010474, A179638.

Programs

Mathematica

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

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.