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A236367 Dihedral angle in a regular icosahedron (radians). 4
2, 4, 1, 1, 8, 6, 4, 9, 9, 7, 3, 6, 2, 8, 2, 6, 8, 7, 5, 0, 0, 7, 8, 4, 6, 7, 2, 3, 4, 6, 6, 1, 8, 2, 1, 8, 8, 8, 0, 0, 6, 6, 3, 4, 8, 5, 3, 2, 7, 3, 9, 2, 1, 3, 0, 2, 6, 5, 9, 9, 5, 1, 0, 0, 8, 4, 5, 9, 9, 7, 5, 0, 6, 6, 1, 9, 4, 4, 1, 8, 5, 9, 8, 3, 2, 5, 5, 1, 4, 1, 7, 5, 2, 2, 6, 4, 3, 5, 6, 7, 7, 7, 4, 0, 5 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Wikipedia, Platonic solid.
FORMULA
Equals 2*arctan(phi^2) = 2*arctan(A001622^2) = 2*arctan((3+sqrt(5))/2).
EXAMPLE
2.41186499736282687500784672346618218880066348532739213...
MATHEMATICA
RealDigits[2 * ArcTan[GoldenRatio^2], 10, 120][[1]] (* Amiram Eldar, May 17 2023 *)
PROG
(PARI) 2*atan((3+sqrt(5))/2)
CROSSREFS
Cf. A001622, Platonic solids dihedral angles: A137914 (tetrahedron), A156546 (octahedron), A019669 (cube), A137218 (dodecahedron).
Sequence in context: A329458 A332010 A201287 * A197489 A297966 A103161
KEYWORD
nonn,cons,easy
AUTHOR
Stanislav Sykora, Jan 23 2014
STATUS
approved

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Last modified March 19 01:57 EDT 2024. Contains 370952 sequences. (Running on oeis4.)