This one, by Dr. Titu Andreescu (of USAMO fame), is elementary in the sense that the solution to the problem doesn’t require anything more than arguments involving parity and congruences. I have the solution with me but I won’t post it on my blog until Jan 19, 2008, which is when the deadline for submission is. By the way, the problem (in the senior section) is from the 6^{th} issue of Mathematical Reflections, 2007.

Problem: Find the least odd positive integer n such that for each prime \displaystyle p, \, \frac{n^2-1}{4} + np^4 + p^8 is divisible by at least four (distinct) primes.

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