%N Decimal expansion of the site percolation threshold for the (3, 12^2) Archimedean lattice.
%C From the Wikipedia article (see link):
%C "Percolation threshold is a mathematical term related to percolation theory, which is the formation of long-range connectivity in random systems. Below the threshold a giant connected component does not exist while above it, there exists a giant component of the order of system size. In engineering and coffee making, percolation represents the flow of fluids through porous media, but in the mathematics and physics worlds it generally refers to simplified lattice models of random systems or networks (graphs), and the nature of the connectivity in them. The percolation threshold is the critical value of the occupation probability p, or more generally a critical surface for a group of parameters p_1,p_2, ..., such that infinite connectivity (percolation) first occurs."
%D Suding, P. N.; R. M. Ziff (1999). "Site percolation thresholds for Archimedean lattices". Physical Review E 60 (1): 275-283. Bibcode 1999PhRvE..60..275S. doi:10.1103/PhysRevE.60.275
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Percolation_threshold">Percolation threshold</a>, as downloaded Dec 22 2012
%F (1 - 2 sin (pi/18))^(1/2).
%A _Jonathan Vos Post_, Dec 22 2012