A385261 Decimal expansion of the surface area of a gyroelongated pentagonal bicupola with unit edge.

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

Offset

2,1

Comments

The gyroelongated pentagonal bicupola is Johnson solid J_46.

Links

Paolo Xausa, Table of n, a(n) for n = 2..10000

Wikipedia, Gyroelongated pentagonal bicupola.

Formula

Equals (20 + 15*sqrt(3) + sqrt(25 + 10*sqrt(5)))/2 = (20 + 15*A002194 + sqrt(25 + 10*A002163))/2.

Equals the largest root of x^8 - 80*x^7 + 2100*x^6 - 14000*x^5 - 174750*x^4 + 1390000*x^3 + 9603125*x^2 + 9937500*x - 6546875.

Example

26.431335857944513546973871516071261950885787743598...

Mathematica

First[RealDigits[(20 + 15*Sqrt[3] + Sqrt[25 + 10*Sqrt[5]])/2, 10, 100]] (* or *)
First[RealDigits[PolyhedronData["J46", "SurfaceArea"], 10, 100]]

Crossrefs

Cf. A385260 (volume).

Cf. A002163, A002194, A384284, A385257, A385259.

Sequence in context: A283614 A333520 A395732 * A003571 A068457 A394397

Adjacent sequences: A385258 A385259 A385260 * A385262 A385263 A385264

Keyword

nonn,cons,easy

Author

Paolo Xausa, Jun 27 2025

Status

approved