Primality proof for n = 42307:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=641.html>641 is prime.</a>
<br>b^((n-1)/641)-1 mod n = 2665, which is a unit, inverse 42180.
<p>(641) divides n-1.
<p>(641)^2 > n.
<p>n is prime by Pocklington's theorem.