A377698 Decimal expansion of 30*arcsin(sqrt(5)/3).

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

Offset: 2

Author

Paolo Xausa, Nov 05 2024

Keywords

• nonn
• cons
• easy

Comments

Dehn invariant of a regular icosahedron with unit edge length and (negated) of a truncated dodecahedron with unit edge length.

Examples

			25.232060117037907673295750954792922401062363569...
		

Links

• Brady Haran and Daniel Litt, The Dehn Invariant, Numberphile YouTube video, 2019.
• Eric Weisstein's World of Mathematics, Dehn Invariant.
• Eric Weisstein's World of Mathematics, Regular Icosahedron.
• Eric Weisstein's World of Mathematics, Truncated Dodecahedron.
• Wikipedia, Dehn Invariant.
• Index entries for transcendental numbers

Crossrefs

Cf. A228496.

Programs

Mathematica

First[RealDigits[30*ArcCos[2/3], 10, 100]] (* or *)
First[RealDigits[PolyhedronData["Icosahedron", "DehnInvariant"], 10, 100]]

PARI

30*acos(2/3) \\ Charles R Greathouse IV, Nov 21 2024

Formula

Equals 30*arccos(2/3) = 30*A228496.