Primality proof for n = 3943:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=73.html>73 is prime.</a>
<br>b^((n-1)/73)-1 mod n = 1405, which is a unit, inverse 2015.
<p>(73) divides n-1.
<p>(73)^2 > n.
<p>n is prime by Pocklington's theorem.