OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Pentagon
FORMULA
Equals sqrt(25 + 10*sqrt(5)) / 4.
Equals (3*phi+1)*sqrt(3-phi) with the golden section phi = (1 + sqrt(5))/2. - Wolfdieter Lang, Jan 25 2013
Equals 5/(4*tan(Pi/5)). - Michel Marcus, Mar 25 2015
Equals (5/4)*sqrt(phi^3/sqrt(5)). - G. C. Greubel, Jul 03 2017
EXAMPLE
1.720477400588966922759011977...
MATHEMATICA
RealDigits[(5/4)*Sqrt[GoldenRatio^3/Sqrt[5]], 10, 50][[1]] (* G. C. Greubel, Jul 03 2017 *)
PROG
(PARI) 5/(4*tan(Pi/5)) \\ Michel Marcus, Mar 25 2015
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Bryan Jacobs (bryanjj(AT)gmail.com), Feb 10 2005
EXTENSIONS
Corrected the title. - Stanislav Sykora, Apr 12 2015
STATUS
approved