A384215 Decimal expansion of the surface area of a gyroelongated square cupola with unit edge.

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

Offset: 2

Author

Paolo Xausa, May 23 2025

Keywords

• nonn
• cons
• easy

Comments

The gyroelongated square cupola is Johnson solid J_23.

Examples

			18.4886811625905765652406091559487579918533700198...
		

Links

• Paolo Xausa, Table of n, a(n) for n = 2..10000
• Wikipedia, Gyroelongated square cupola.

Crossrefs

Cf. A384214 (volume).

Cf. A002194, A010466.

Programs

Mathematica

First[RealDigits[7 + Sqrt[8] + Sqrt[75], 10, 100]] (* or *)
First[RealDigits[PolyhedronData["J23", "SurfaceArea"], 10, 100]]

Formula

Equals 7 + 2*sqrt(2) + 5*sqrt(3) = 7 + A010466 + 5*A002194.

Equals the largest root of x^4 - 28*x^3 + 128*x^2 + 952*x - 1244.