A384624 Decimal expansion of the volume of a pentagonal orthobicupola with unit edge.

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

Offset

1,1

Comments

The pentagonal orthobicupola is Johnson solid J_30.

Also the volume of a pentagonal gyrobicupola (Johnson solid J_31) with unit edge.

Links

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

Wikipedia, Pentagonal orthobicupola.

Wikipedia, Pentagonal gyrobicupola.

Formula

Equals (5 + 4*sqrt(5))/3 = (5 + A010532)/3.

Equals the largest root of 9*x^2 - 30*x - 55.

Example

4.6480906366663862618788982249750349805874911461487...

Mathematica

First[RealDigits[(5 + Sqrt[80])/3, 10, 100]] (* or *)
First[RealDigits[PolyhedronData["J30", "Volume"], 10, 100]]

Crossrefs

Cf. A384625 (surface area).

Cf. A010532, A384287.

Sequence in context: A084892 A344475 A245556 * A256318 A018835 A055166

Adjacent sequences: A384621 A384622 A384623 * A384625 A384626 A384627

Keyword

nonn,cons,easy

Author

Paolo Xausa, Jun 05 2025

Status

approved