OFFSET
1,1
LINKS
Matthew House, Table of n, a(n) for n = 1..10000
F. Fodor, The densest packing of 12 congruent circles in a circle, Beiträge zur Algebra und Geometrie / Contributions to Algebra and Geometry, 41 (2000), No. 2, 401-409.
FORMULA
Set r as the greatest real root of x^5 - 3*x^4 + 7*x^2 - 15*x + 9 = 0. Then, A = 1 + 2*r/sqrt(3) = 4.029601930...
EXAMPLE
4.029601930116183497482741041263349896...
MATHEMATICA
r = Root[#^5 - 3 #^4 + 7 #^2 - 15 # + 9 &, 3];
N[1 + 2 r/Sqrt[3], 20]
PROG
(PARI) r = solve(x=2, 3, x^5 - 3*x^4 + 7*x^2 - 15*x + 9); 1 + 2*r/sqrt(3) \\ Michel Marcus, Feb 11 2017
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Matthew House, Feb 10 2017
STATUS
approved