A391656 Decimal expansion of the dihedral angle, in radians, between two adjacent pentagonal faces (meeting at their longest edge) in a Dürer's solid.

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

Offset

1,2

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(2 - sqrt(5)) = arccos(2 - A002163).

Equals Pi - A238238.

Example

1.8091137886047627282546335913239174428621891219232...

Mathematica

First[RealDigits[ArcCos[2 - Sqrt[5]], 10, 100]] (* or *)
First[RealDigits[RankedMax[Union[PolyhedronData["DuererSolid", "DihedralAngles"]], 2], 10, 100]]

Crossrefs

Cf. other dihedral angles: A238238, A391657.

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

Cf. A080992, A002163.

Sequence in context: A019863 A350747 A243456 * A246772 A198820 A138285

Adjacent sequences: A391653 A391654 A391655 * A391657 A391658 A391659

Keyword

nonn,cons,easy

Author

Paolo Xausa, Dec 16 2025

Status

approved