I once read a short paper on the following subject. Fix a graph $H$ with fractional coloring number $c$ and let $G$ be a graph with $n$ vertices and $e$ edges, with $e$,$n$ large. In terms of $n$, $e$, and $c$, we want to bound from above and below the number of homomorphisms from $H$ to $G$.
I cannot seem to find the paper. Can someone help me?
I don't remember the authors, but they thanked Gil Kalai for suggesting the connection with fractional coloring number; this is a detail that I remember, for some reason.