Fix filter no-n-aps, since it did not work
Fix filter no-n-aps, since it did not work

I am (fairly) confident that it is doing the right thing now,
in that it searches all possible gap sizes (and maybe a couple
more), and has no more fencepost errors.

It correctly calculates the numbers w(3;2), w(4;2) and w(5;2).

apoelstra/RamseyScript,apoelstra/RamseyScript