(In reply to
a twist, perhaps? by DJ)
My solution is complete, although my final explanation probably didn't make it very clear.
Suppose you have the equation
ab=cd
where you know the following:
a, b, c, and d are integers
b is prime
b is not equal to c or d
Thus, since b is prime it must be a factor of either c or d, giving an equation:
a=(c/b)d OR a=c(d/b)
In either case, since b is not equal to c or d, both terms on the right must evaluate to integers greater then 1, and we know that a cannot be prome.
This is the situation in my solution. I have derived the equation:
101(1 + 10^4 + 10^8 + ... + 10^4i) = (1 + 10^2 + 10^4 + ... + 10^2i)(10^(2i_2) +1)
In which 101 is prime, and neither of the lefthand members is equal to 101 when i>1. Therefore, by the same reasoning described above, we know that all numbers of the form
1 + 10^4 + 10^8 + ... + 10^4i
are not prime (when i=1, the equation becomes 101(10001)=101(10001), which proves nothing, but 10001=73(137), so it is also not prime).

Posted by DJ
on 20030525 04:46:47 