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%I #22 Dec 27 2021 20:58:02
%S 3,5,8,3,6,7,9,4,9,5,4,5,3,0,0,2,7,3,4,8,4,1,3,7,7,8,9,4,1,3,4,6,6,8,
%T 3,4,1,9,1,5,4,4,4,4,9,4,6,0,0,1,3,7,9,5,4,6,3,5,7,6,7,7,5,8,5,7,3,1,
%U 9,9,2,5,9,8,2,4,9,9,0,9,8,9,8,7,3,1,6,0,9,1,3,9,2,9,8,6,7,8,9
%N Decimal expansion of sine of 21 degrees.
%H Ivan Panchenko, <a href="/A019830/b019830.txt">Table of n, a(n) for n = 0..1000</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Trigonometric_constants_expressed_in_real_radicals">Trigonometric constants expressed in real radicals</a>
%F Equals A019823*A019892 + A019816*A019885 = A019827*A019896 + A019812*A019881. - _R. J. Mathar_, Jan 27 2021
%t RealDigits[Sin[21 Degree],10,120][[1]] (* _Harvey P. Dale_, Apr 06 2016 *)
%o (PARI) sin(7*Pi/60) \\ _Charles R Greathouse IV_, Jan 30 2016
%Y Cf. A019812, A019816, A019823, A019827, A019881, A019892, A019885, A019896.
%K nonn,cons
%O 0,1
%A _N. J. A. Sloane_