Let f(z) = exp\(\rm\left(z+\frac{1}{z}\right)\), z ∈ ℂ\{0}. The residue of f at z = 0 is
1
\(\sum_{l=0}^{\infty} \frac{1}{(l+1) !}\)
2
\(\sum_{l=0}^{\infty} \frac{1}{l !(l+1)}\)
3
\(\sum_{l=0}^{\infty} \frac{1}{l !(l+1) !}\)
4
\(\sum_{l=0}^{\infty} \frac{1}{\left(l^2+l\right) !}\)