A390143 - OEIS

%I #7 Oct 30 2025 18:30:44

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

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

%U 5,2,2,8,0,6,4,7,0,4,4,7,0,5,4,0,8,2,5,0,8,6

%N Decimal expansion of the smallest dihedral angle, in radians, in a snub disphenoid (Johnson solid J_84).

%H Paolo Xausa, <a href="/A390143/b390143.txt">Table of n, a(n) for n = 1..10000</a>

%H Polytope Wiki, <a href="https://polytope.miraheze.org/wiki/Snub_disphenoid">Snub disphenoid</a>.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Snub_disphenoid">Snub disphenoid</a>.

%F Equals arccos(c/3), where c is the largest root of x^3 + 25*x^2 + 79*x + 23.

%e 1.6789775749362604980287408653316751544832594225595...

%t First[RealDigits[ArcCos[Root[#^3 + 25*#^2 + 79*# + 23 &, 3]/3], 10, 100]] (* or *)

%t First[RealDigits[Min[PolyhedronData["J84", "DihedralAngles"]], 10, 100]]

%Y Cf. other J_84 dihedral angles: A390144, A390145.

%Y Cf. A386695 (J_84 volume), A010482 (J_84 surface area).

%K nonn,cons,easy

%O 1,2

%A _Paolo Xausa_, Oct 28 2025