password/passphrase generation

[Gerald Combs]

On Thu, 5 Jun 2003, David Holland wrote:

> > What number does not belong?  < 1 2 3 4 5 >  And why does it not
> belong?
> >
> 
> I'm guessing 4 because all others are prime...?

1 isn't prime either:

    http://www.utm.edu/research/primes/notes/faq/one.html

There are a couple of other arguments for 4, however:

  - < 1 2 3 5 > is part of the Fibonacci sequence.

  - 4 is the only one in the list whose square root is a whole number
    not equal to itself.