[EM] Divisor method equivalence

[Kristofer Munsterhjelm]

Hello all,

Could someone show me a proof of how the Sainte-Laguë and Webster's 
method are equivalent? On the surface of it, each method has an approach 
that's quite different from the other: Sainte-Laguë divides subsequently 
by (1, 3, 5, 7, etc), while Webster's finds the correct 
divisor/multiplier for all in one go.

In general, what is the relation between the divisors in a 
highest-average method and the rounding in the equivalent "find divisor 
so that the rounded numbers sum up to what we want" method?