GCD question

[David Wilson]

Could someone mail me the math-fun addy?

In the meantime, I'm sending this to seqfan under the assumption that there
is a lot of crossover between the two groups.

Let x, y > 0 with (x, y) = 1.

Then c = xy is the largest integer not of the form ax+by where a, b > 0.

If we add the further condition (a, b) = 1, does such a c then necessarily
exist, and if so, can we bound it?