OFFSET
0,1
COMMENTS
Also the decimal expansion of cotangent of 54 degrees. - Mohammad K. Azarian, Jun 30 2013
A quartic integer. - Charles R Greathouse IV, Aug 27 2017
LINKS
Ivan Panchenko, Table of n, a(n) for n = 0..1000
Wikipedia, Exact trigonometric constants
FORMULA
This number is sqrt(5-2*sqrt(5)). This number * A019970 = sqrt(5) = A002163. - R. J. Mathar, Jun 18 2006
The smallest positive solution of cos(4*arctan(x)) = cos(6*arctan(x)). - Thomas Olson, Oct 03 2014
Let r(n) = (n - 1)/(n + 1) if n mod 4 = 1, (n + 1)/(n - 1) otherwise; then this constant (A019934) equals with Product_{n>=0} r(10*n+5) = (2/3) * (8/7) * (12/13) * (18/17) * ... - Dimitris Valianatos, Sep 14 2019
MATHEMATICA
RealDigits[Tan[36 Degree], 10, 120][[1]] (* Harvey P. Dale, Nov 06 2012 *)
PROG
(PARI) tan(Pi/5) \\ Charles R Greathouse IV, Aug 27 2017
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
STATUS
approved