0,1

Equals the absolute value of the cosine of the dihedral angle between two adjacent faces of the regular icosahedron.

Ivan Panchenko, Table of n, a(n) for n = 0..1000

Wikipedia, Exsphere

Equals A002163/3 = 20*A020837/3

0.7453559924...

RealDigits[Sqrt[5]/3, 10, 120][[1]] (* Harvey P. Dale, Jul 03 2013 *)

Sequence in context: A011475 A180078 A019685 * A087491 A019899 A085662

Adjacent sequences: A208896 A208897 A208898 * A208900 A208901 A208902

nonn,cons,easy

R. J. Mathar, Mar 03 2012

approved