A391657 Decimal expansion of the dihedral angle, in radians, between a pentagonal face and a triangular face in a Dürer's solid.

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

Offset

1,1

Comments

The value of this constant is based on the interpretation of Dürer's solid given in A391653. See there for more information and links.

Links

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

Formula

Equals arccos(-sqrt((5 - 2*sqrt(5))/3)) = arccos(-sqrt((5 - A010476)/3)).

Example

2.003657194977058543083198442643046488359003044008...

Mathematica

First[RealDigits[ArcCos[-Sqrt[(5 - Sqrt[20])/3]], 10, 100]] (* or *)
First[RealDigits[Max[PolyhedronData["DuererSolid", "DihedralAngles"]], 10, 100]]

Crossrefs

Cf. other dihedral angles: A238238, A391656.

Cf. A391653 (volume), A391654 (surface area), A391655 (circumradius).

Cf. A080992, A010476.

Sequence in context: A244120 A277536 A348849 * A351142 A269159 A388475

Adjacent sequences: A391654 A391655 A391656 * A391658 A391659 A391660

Keyword

nonn,cons,easy

Author

Paolo Xausa, Dec 16 2025

Status

approved