A378976 Decimal expansion of the midradius of a triakis icosahedron with unit shorter edge length.

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

Offset

1,2

Comments

The triakis icosahedron is the dual polyhedron of the truncated dodecahedron.

Links

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

Eric Weisstein's World of Mathematics, Triakis Icosahedron.

Wikipedia, Triakis icosahedron.

Formula

Equals 1/2 + 2/sqrt(5) = 1/2 + 2/A002163.

Equals (A249600 + 13)/10 = (A010532 + 5)/10.

Example

1.3944271909999158785636694674925104941762473438446...

Mathematica

First[RealDigits[1/2 + 2/Sqrt[5], 10, 100]] (* or *)
First[RealDigits[PolyhedronData["TriakisIcosahedron", "Midradius"], 10, 100]]

Crossrefs

Cf. A378973 (surface area), A378974 (volume), A378975 (inradius), A378977 (dihedral angle).

Cf. A377697 (midradius of a truncated dodecahedron with unit edge length).

Cf. A002163, A010532, A249600.

Sequence in context: A321120 A243711 A247553 * A307238 A161773 A212992

Adjacent sequences: A378973 A378974 A378975 * A378977 A378978 A378979

Keyword

nonn,cons,easy

Author

Paolo Xausa, Dec 14 2024

Status

approved