
Originally Posted by
YesNo
The link on factorials and triangular numbers gives a proof of what you were trying to show for even factorials. Basically, think of a triangular number written in closed form. That is, the sum of the first n numbers can be represented by n(n+1)/2. Since we skip the even triangular numbers and get rid of the 2 in the denominator with the 2n/2 factor, this looks like it should prove the result.
I am beginning to understand the abc conjecture. Take relatively prime integers a + b = c. Define rad(abc) = rad(a)rad(b)rad(c) to be a product of the unique primes in the product abc. This product is typically larger than c, but sometimes it is not. Sometimes rad(abc) < c and there are infinitely many triples (a,b,c) such that rad(abc) < c. However, there are (so I hear) no known example where (rad(abc))2 < c. That is if we raise rad(abc) to some power larger than 1, no matter how small that "larger than one is", then we get only finitely many triples that would work, that is, (rad(abc))1+epsilon < c has only finitely many triples (a, b, c) for which that relationship holds.
That is the abc conjecture. For this to apply to Brocard's problem, we would need to establish that for all n, n! + 1 = m2 is such that (rad(n!)rad(1)rad(m2))1+epsilon is always less than m2 for some epsilon. Of course, I might be misunderstanding all of this.