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Ivan Panchenko, Table of n, a(n) for n = 0..1000
Wikipedia, Exact trigonometric constants
RealDigits[Sin[21 Degree], 10, 120][] (* Harvey P. Dale, Apr 06 2016 *)
(PARI) sin(7*Pi/60) \\ Charles R Greathouse IV, Jan 30 2016
Sequence in context: A181918 A010617 A016659 * A259238 A094355 A087334
Adjacent sequences: A019827 A019828 A019829 * A019831 A019832 A019833
N. J. A. Sloane.