A385488 Decimal expansion of the surface area of a gyroelongated pentagonal birotunda with unit edge.

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

Offset

2,1

Comments

The gyroelongated pentagonal birotunda is Johnson solid J_48.

Links

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

Wikipedia, Gyroelongated pentagonal birotunda.

Formula

Equals 10*sqrt(3) + 3*sqrt(25 + 10*sqrt(5)) = 10*A002194 + 3*sqrt(25 + 10*A002163).

Equals the largest root of x^8 - 2100*x^6 + 1032750*x^4 - 121162500*x^2 + 1216265625.

Example

37.966236882756376008382607143722038862316542578226...

Mathematica

First[RealDigits[10*Sqrt[3] + 3*Sqrt[25 + 10*Sqrt[5]], 10, 100]] (* or *)
First[RealDigits[PolyhedronData["J48", "SurfaceArea"], 10, 100]]

Crossrefs

Cf. A385264 (volume).

Cf. A002163, A002194, A384284, A385261, A385263.

Sequence in context: A388222 A385230 A342354 * A011271 A005534 A113014

Adjacent sequences: A385485 A385486 A385487 * A385489 A385490 A385491

Keyword

nonn,cons,easy

Author

Paolo Xausa, Jun 30 2025

Status

approved