function [ret divs]=crux1746(B)
%{
Find infinitely many pairs of integers a and b
with 1 < a < b, so that ab exactly divides
a^2 + b^2 ? 1.
(b) With a and b as above, what are the
possible values of (a^2 + b^2 ? 1)/(ab) ?
%}
[X,Y]=meshgrid(2:B,2:B);
X=X(:);
Y=Y(:);
XY=[X Y];
I = X