A395168 - OEIS

%I #16 May 22 2026 07:55:38

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

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

%U 1,5,4,9,1,6,3,3,3,6,6,7,2,2,7,7,7,1,7,3,6,4

%N Decimal expansion of the height of a uniform 9-gonal antiprism with unit edges.

%H Paolo Xausa, <a href="/A395168/b395168.txt">Table of n, a(n) for n = 0..10000</a>

%H Polytope Wiki, <a href="https://polytope.miraheze.org/wiki/Enneagonal_antiprism">Enneagonal antiprism</a>.

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Antiprism.html">Antiprism</a>.

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

%H <a href="/index/Al#algebraic_06">Index entries for algebraic numbers, degree 6</a>.

%F Equals sqrt(1 - (sec(Pi/18)^2)/4).

%F Equals sqrt((1 + 2*cos(Pi/9))/(2 + 2*cos(Pi/9))) = sqrt((1 + A332437)/(2 + A332437)).

%F Equals the largest real root of 3*x^6 - 3*x^2 + 1.

%e 0.861526087224617450394219811772086466962778416440...

%t First[RealDigits[Sqrt[1 - (Sec[Pi/18]^2)/4], 10, 100]]

%Y Cf. A395164 (volume), A395165 (surface area), A395166 (midradius), A395167 (circumradius).

%Y Cf. A395169, A395170 (dihedral angles).

%Y Cf. A332437.

%K nonn,cons,easy

%O 0,1

%A _Paolo Xausa_, Apr 24 2026