A380705 Decimal expansion of the obtuse vertex angle, in radians, in a deltoidal icositetrahedron face.

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

Offset: 1

Author

Paolo Xausa, Jan 31 2025

Keywords

• nonn
• cons
• easy

Examples

			2.0117218987854118285886146965582917137369448278649...
		

Links

• Paolo Xausa, Table of n, a(n) for n = 1..10000
• Wikipedia, Deltoidal icositetrahedron.

Crossrefs

Cf. A380704 (face acute angles).

Cf. A020789, A378390, A378391, A378392, A378393, A378394.

Programs

Mathematica

First[RealDigits[ArcCos[-1/4 - Sqrt[2]/8], 10, 100]]

Formula

Equals arccos(-1/4 - sqrt(2)/8) = arccos(-1/4 - A020789).

Equals 2*Pi - 3*A380704.