OFFSET
1,1
COMMENTS
The ratio of the perimeter of a regular 9-gon (nonagon) to its diameter (largest diagonal).
Also least positive root of x^3 - 243x + 729.
FORMULA
18*A019819.
EXAMPLE
3.125667198004746279330899281847666328006762189313248970252344806377184798...
MAPLE
evalf(18*sin(Pi/18), 100); # Wesley Ivan Hurt, Feb 01 2017
MATHEMATICA
RealDigits[18*Sin[Pi/18], 10, 120][[1]] (* Harvey P. Dale, Dec 02 2018 *)
PROG
(PARI) 18*sin(Pi/18)
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Rick L. Shepherd, Jan 06 2017
STATUS
approved