Primality proof for n = 4211:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=421.html>421 is prime.</a>
<br>b^((n-1)/421)-1 mod n = 1023, which is a unit, inverse 2017.
<p>(421) divides n-1.
<p>(421)^2 > n.
<p>n is prime by Pocklington's theorem.