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 A272536 Decimal expansion of the edge length of a regular 20-gon with unit circumradius. 4
 3, 1, 2, 8, 6, 8, 9, 3, 0, 0, 8, 0, 4, 6, 1, 7, 3, 8, 0, 2, 0, 2, 1, 0, 6, 3, 8, 9, 3, 4, 3, 3, 3, 7, 8, 4, 6, 2, 7, 7, 9, 9, 7, 8, 4, 1, 7, 1, 3, 2, 1, 5, 8, 0, 1, 6, 9, 2, 8, 2, 6, 9, 2, 1, 1, 5, 5, 1, 7, 5, 8, 6, 6, 1, 1, 2, 4, 7, 1, 5, 8, 6, 7, 3, 3, 9, 1, 7, 4, 5, 3, 5, 3, 6, 9, 7, 3, 7, 6, 7, 5, 0, 2, 8, 0 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Since 20-gon is constructible (see A003401), this is a constructible number. LINKS Stanislav Sykora, Table of n, a(n) for n = 0..2000 Mauro Fiorentini, Construibili (numeri) Eric Weisstein's World of Mathematics, Constructible Number Wikipedia, Constructible number Wikipedia, Regular polygon FORMULA Equals 2*sin(Pi/20) = 2*A019818. Equals also (sqrt(2)+sqrt(10)-2*sqrt(5-sqrt(5)))/4. EXAMPLE 0.3128689300804617380202106389343337846277997841713215801692826921... MATHEMATICA RealDigits[N[2Sin[Pi/20], 100]][[1]] (* Robert Price, May 02 2016*) PROG (PARI) 2*sin(Pi/20) CROSSREFS Cf. A003401. Edge lengths of other constructible m-gons: A002194 (m=3), A002193 (4), A182007 (5), A101464 (8), A094214 (10), A101263 (12), A272534 (15), A272535 (16), A228787 (17). Cf. A019818. Sequence in context: A204128 A266272 A201677 * A204122 A201657 A279384 Adjacent sequences:  A272533 A272534 A272535 * A272537 A272538 A272539 KEYWORD nonn,cons,easy AUTHOR Stanislav Sykora, May 02 2016 STATUS approved

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Last modified June 26 20:17 EDT 2022. Contains 354885 sequences. (Running on oeis4.)