A390144 Decimal expansion of the second smallest dihedral angle, in radians, in a snub disphenoid (Johnson solid J_84).

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

Offset

1,1

Links

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

Polytope Wiki, Snub disphenoid.

Wikipedia, Snub disphenoid.

Formula

Equals arccos(c), where c is the largest negative root of 27*x^3 + 27*x^2 - 75*x - 43.

Example

2.1248189366147042378417781962115166356186320982755...

Mathematica

First[RealDigits[ArcCos[Root[27*#^3 + 27*#^2 - 75*# - 43 &, 2]], 10, 100]] (* or *)
First[RealDigits[RankedMin[Union[PolyhedronData["J84", "DihedralAngles"]], 2], 10, 100]]

Crossrefs

Cf. other J_84 dihedral angles: A390143, A390145.

Cf. A386695 (J_84 volume), A010482 (J_84 surface area).

Sequence in context: A275762 A350626 A139248 * A138380 A016013 A193384

Adjacent sequences: A390141 A390142 A390143 * A390145 A390146 A390147

Keyword

nonn,cons,easy

Author

Paolo Xausa, Oct 28 2025

Status

approved