Primality proof for n = 19603:
<p>Take b = 2.
<p>b^(n-1) mod n = 1.
<p><a href=11.html>11 is prime.</a>
<br>b^((n-1)/11)-1 mod n = 3727, which is a unit, inverse 5002.
<p><a href=3.html>3 is prime.</a>
<br>b^((n-1)/3)-1 mod n = 9870, which is a unit, inverse 16312.
<p>(3^4 * 11^2) divides n-1.
<p>(3^4 * 11^2)^2 > n.
<p>n is prime by Pocklington's theorem.