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 A019916 Decimal expansion of tan(Pi/10) (angle of 18 degrees). 1
 3, 2, 4, 9, 1, 9, 6, 9, 6, 2, 3, 2, 9, 0, 6, 3, 2, 6, 1, 5, 5, 8, 7, 1, 4, 1, 2, 2, 1, 5, 1, 3, 4, 4, 6, 4, 9, 5, 4, 9, 0, 3, 4, 7, 1, 5, 2, 1, 4, 7, 5, 1, 0, 0, 3, 0, 7, 8, 0, 4, 7, 1, 9, 1, 3, 6, 6, 7, 2, 9, 0, 0, 9, 6, 0, 7, 4, 4, 9, 4, 8, 3, 2, 2, 6, 8, 7, 7, 3, 5, 4, 4, 6, 9, 6, 5, 0, 5, 0 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS In a regular pentagon inscribed in a unit circle this is the cube of the length of the side divided by 5: (1/5)*(sqrt(3 - phi))^3 with phi from A001622. - Wolfdieter Lang, Jan 08 2018 Quartic number of denominator 5 and minimal polynomial 5x^4 - 10x^2 + 1. - Charles R Greathouse IV, May 13 2019 LINKS Ivan Panchenko, Table of n, a(n) for n = 0..1000 Wikipedia, Exact trigonometric constants FORMULA Equals A019827/A019881 = 1/A019970 = 1/sqrt(5+2*sqrt(5)). - R. J. Mathar, Jul 26 2010 Equals tan((phi - 1)/sqrt(2 + phi)) = (1/5)*(sqrt(3 - phi))^3 = (3 - phi)*sqrt(3 - phi)/5 = sqrt(7 - 4*phi)/(2*phi - 1), with phi from A001622. - Wolfdieter Lang, Jan 08 2018 EXAMPLE 0.3249196962329063261558714122151344649549034715214751003078047191... MATHEMATICA RealDigits[Tan[18 Degree], 10, 120][[1]] (* Harvey P. Dale, Mar 07 2012 *) PROG (PARI) tan(Pi/10) \\ Michel Marcus, Jan 08 2018 CROSSREFS Cf. A001622, A019827 (sin(Pi/10)), A019881 (cos(Pi/10)). Sequence in context: A084657 A171559 A300883 * A201838 A099257 A270701 Adjacent sequences:  A019913 A019914 A019915 * A019917 A019918 A019919 KEYWORD nonn,cons,changed AUTHOR STATUS approved

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Last modified May 23 03:10 EDT 2019. Contains 323507 sequences. (Running on oeis4.)