With a given set $A=\{{0,...,N\}}$ we can choose only $H$ numbers from it (we can pick same number many times), And put them in a row. The sum of those numbers has to be some given $X$. The first element in any row can't be $0$.
For example for the set $A=\{{0,1,2,3\}}$, $X=3$ and $H=4$
we can have such variations:
1110
1011
1101
1200
1020
1002
3000
But we can't form: $0003$ and other silimar.
How many such variations can we produce from given $X$, $N$ and $H$?