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A208899
Decimal expansion of sqrt(5)/3.
3
7, 4, 5, 3, 5, 5, 9, 9, 2, 4, 9, 9, 9, 2, 9, 8, 9, 8, 8, 0, 3, 0, 5, 7, 8, 8, 9, 5, 7, 7, 0, 9, 2, 0, 7, 8, 4, 8, 0, 2, 0, 6, 1, 1, 9, 8, 7, 0, 5, 0, 8, 5, 7, 4, 7, 5, 6, 9, 6, 5, 7, 4, 8, 4, 7, 0, 1, 7, 3, 6, 4, 1, 8, 7, 9, 2, 6, 8, 2, 9, 9, 8, 0, 4, 8, 0, 4, 8, 0, 2, 7, 9, 2, 9, 2, 7, 4, 2, 4, 9
OFFSET
0,1
COMMENTS
Equals the absolute value of the cosine of the dihedral angle between two adjacent faces of the regular icosahedron.
LINKS
Mathematics Stack Exchange, Maximum and Minimum Value of f(x)
Michael Penn, an "extreme" extreme value problem., YouTube video, 2022.
Wikipedia, Exsphere
FORMULA
Equals A002163/3 = 20*A020837/3.
Equals Sum_{k>=0} (-1)^k * binomial(2*k,k)/5^k. - Amiram Eldar, Aug 03 2020
EXAMPLE
0.7453559924...
MATHEMATICA
RealDigits[Sqrt[5]/3, 10, 120][[1]] (* Harvey P. Dale, Jul 03 2013 *)
PROG
(PARI) first(n) = default(realprecision, max(28, n+10)); digits(((sqrt(5)/3)*10^n)\1) \\ David A. Corneth, Dec 19 2022
CROSSREFS
Sequence in context: A011475 A180078 A019685 * A087491 A019899 A357100
KEYWORD
nonn,cons,easy
AUTHOR
R. J. Mathar, Mar 03 2012
STATUS
approved