Primality proof for n = 1811:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=181.html>181 is prime.</a>
<br>b^((n-1)/181)-1 mod n = 1023, which is a unit, inverse 1680.
<p>(181) divides n-1.
<p>(181)^2 > n.
<p>n is prime by Pocklington's theorem.