Primality proof for n = 15217:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=317.html>317 is prime.</a>
<br>b^((n-1)/317)-1 mod n = 7359, which is a unit, inverse 3019.
<p>(317) divides n-1.
<p>(317)^2 > n.
<p>n is prime by Pocklington's theorem.