A384287 Decimal expansion of the volume of a square orthobicupola with unit edge.

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

Offset: 1

Author

Paolo Xausa, Jun 05 2025

Keywords

• nonn
• cons
• easy

Comments

The square orthobicupola is Johnson solid J_28.

Also the volume of a square gyrobicupola (Johnson solid J_29) with unit edge.

Examples

			3.885618083164126731735584965612930771426229167169...
		

Links

• Paolo Xausa, Table of n, a(n) for n = 1..10000
• Wikipedia, Square gyrobicupola.
• Wikipedia, Square orthobicupola.

Crossrefs

Cf. A010469 (surface area - 10).

Cf. A002193, A010487, A384624.

Programs

Mathematica

First[RealDigits[2 + Sqrt[32]/3, 10, 100]] (* or *)
First[RealDigits[PolyhedronData["J28", "Volume"], 10, 100]]

Formula

Equals 2 + (4/3)*sqrt(2) = 2 + (4/3)*A002193 = 2 + A010487/3.

Equals the largest root of 9*x^2 - 36*x + 4.