Primality proof for n = 241:
<p>Take b = 7.
<p>b^(n-1) mod n = 1.
<p><a href=5.html>5 is prime.</a>
<br>b^((n-1)/5)-1 mod n = 90, which is a unit, inverse 158.
<p><a href=3.html>3 is prime.</a>
<br>b^((n-1)/3)-1 mod n = 14, which is a unit, inverse 155.
<p><a href=2.html>2 is prime.</a>
<br>b^((n-1)/2)-1 mod n = 239, which is a unit, inverse 120.
<p>(2^4 * 3 * 5) divides n-1.
<p>(2^4 * 3 * 5)^2 > n.
<p>n is prime by Pocklington's theorem.