[OT:] The An paper sizes

Hi,
to put it in formal terms - this is how the format An is defined
(with Xn, Yn being the length and width of an An paper:

X0 * Y0 = 1 m^2 (normalization of the base)
Xn+1 = Yn       (elegant recursion)
Yn+1 = Xn/2

This yields two interesting features:

1) Xn * Yn = 1 m^2 / 2^n
2) Xn / Yn = sqrt(2)

1) establishes a straightforward relation with the metric system.
2) provides the best known irrational number in a measurable way. ;-)

cheers
oliver