A378207 Decimal expansion of the midradius of a triakis tetrahedron with unit shorter edge length.

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

Offset

0,1

Comments

The triakis tetrahedron is the dual polyhedron of the truncated tetrahedron.

Links

Table of n, a(n) for n=0..89.

Index entries for algebraic numbers, degree 2.

Formula

Equals 5/(6*sqrt(2)) = 5/A010524.

Example

0.589255650988789603667370301754040866070696614740...

Mathematica

First[RealDigits[5/Sqrt[72], 10, 100]] (* or *)
First[RealDigits[PolyhedronData["TriakisTetrahedron", "Midradius"], 10, 100]]

Prog

(PARI) 5/sqrt(72) \\ Charles R Greathouse IV, Feb 11 2025

Crossrefs

Cf. A378204 (surface area), A378205 (volume), A378206 (inradius), A378208 (dihedral angle).

Cf. A093577 (midradius of a truncated tetrahedron with unit edge).

Cf. A010524.

Sequence in context: A336266 A241992 A263176 * A197815 A257870 A338275

Adjacent sequences: A378204 A378205 A378206 * A378208 A378209 A378210

Keyword

nonn,cons,easy,changed

Author

Paolo Xausa, Nov 21 2024

Status

approved