Primality proof for n = 250259:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=797.html>797 is prime.</a>
<br>b^((n-1)/797)-1 mod n = 45917, which is a unit, inverse 103631.
<p>(797) divides n-1.
<p>(797)^2 > n.
<p>n is prime by Pocklington's theorem.