Let me introduce the problem.
I have the following functions;
The first one is defined recursively
$h(i,j):=\frac{i-1}{j+1}h(i+2,j-2)$ and $h(i,0)=1$ where $i$ and $j$ are even integers, greater than $0$.
The second one is a sum
$f(n)=\sum_{k=0}^n {n\choose k}\ h(2k,2n-2k)$ where $n$ is a positive integer.
My goal is to find a closed form expression for the function $f(n)$. To implement these functions I have written the following code:
h[i_, 0] := 1
h[i_, j_] := ((j - 1)/(i + 1))*h[i + 2, j - 2]
Sum[Binomial[n, k]*h[2 k, 2 n - 2 k], {k, 0, n}]
But after running this code I am greeted with the following lovely message
$RecursionLimit::reclim2: Recursion depth of 1024 exceeded during evaluation of -2040-2 k+2 n.
I believe there must be an exact formula for the function, based on the physical problem that these functions emerge from. I am hoping that the function $f(n)$ can be written as fraction of polynomials in $n$.
So where is the problem? Is it with my implementation or the functions defined above are hopeless, in the sense that there is no closed form, mathematically?