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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