I've got a little problem, seems simple... Here it is :
We're going to study all couples (n,k) such as :
Let and . Also
So far... :
By replacing the combinations with their formulas with !, i've found that :
So it's easy to show that
And now... ?
I can't find how to show that or :'(
I thought Bézout's identity could help, but no...
Thanks in advance !