The question is
"For a natural number $n$, let $T(n)$ denote the number of ways we can place $n$ objects of weights $1,2,...,n$ on a balance such that the sum of the weights in each pan is the same. Prove that $T(100) > T(99)$."
Now while I have (one of the many possible) solutions thanks to the fact that the people conducting this test released it, though I do not understand one bit of it.
Could someone explain me how to do this question? It's very difficult (for students) as it's part of the Stage I of selection of students from India for the International Mathematics Olympiad.
I am so confused even looking at the question!!!
The solution which was posted was: (scroll down to the last question) http://olympiads.hbcse.tifr.res.in/uploads/crmo-2013-solutions-2
I apologize in advance if this is too simple to search on the Internet.