OFFSET
1,5
COMMENTS
Also the decimal expansion of cotangent of 42 degrees. - Ivan Panchenko, Sep 01 2014
LINKS
Ivan Panchenko, Table of n, a(n) for n = 1..1000
Wikipedia, Exact trigonometric constants
FORMULA
Equals cot(7*Pi/30) = sqrt(23 - 10*sqrt(5) + 2*sqrt(3*(85 -38*sqrt(5)))). - G. C. Greubel, Nov 24 2018
Let r(n) = (n - 1)/(n + 1) if n mod 4 = 1, (n + 1)/(n - 1) otherwise; then this constant equals with Product_{n>=0} r(30*n+15) = (8/7) * (22/23) * (38/37) * (52/53) ... - Dimitris Valianatos, Sep 14 2019
EXAMPLE
1.11061251482919287014348196416513553257695951039085904818440222...
MATHEMATICA
RealDigits[Tan[48 Degree], 10, 120][[1]] (* Harvey P. Dale, Nov 26 2011 *)
RealDigits[Tan[4*Pi/15], 10, 100][[1]] (* G. C. Greubel, Nov 24 2018 *)
PROG
(PARI) default(realprecision, 100); tan(4*Pi/15) \\ G. C. Greubel, Nov 24 2018
(Magma) SetDefaultRealField(RealField(100)); R:= RealField(); Tan(4*Pi(R)/15); // G. C. Greubel, Nov 24 2018
(Sage) numerical_approx(tan(4*pi/15), digits=100) # G. C. Greubel, Nov 24 2018
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
STATUS
approved