0,1

This sequence is also decimal expansion of cosine of 48 degrees. - Mohammad K. Azarian, Jun 29 2013

A quartic number with denominator 2. - Charles R Greathouse IV, Nov 05 2017

Ivan Panchenko, Table of n, a(n) for n = 0..1000

Wikipedia, Exact trigonometric constants

Equals cos (4*Pi/15) = [sqrt(5)-1]*[sqrt(3)*sqrt{5+2*sqrt(5)}-1]/8 = 8*A019887^4 -8*A019887^2+1 = sqrt(1-A019857^2) - R. J. Mathar, Jun 18 2006

(PARI) sin(7/30*Pi) \\ Charles R Greathouse IV, Nov 05 2017

Sequence in context: A083507 A157320 A200616 * A155880 A217852 A021603

Adjacent sequences: A019848 A019849 A019850 * A019852 A019853 A019854

nonn,cons

N. J. A. Sloane.

approved