Fix 1 < a < >\infty.
Consider the random graph G(n,a/n);
so there are n vertices, and each possible edge is present with
probability a/n.
An independent set in a graph is a set of vertices, no two of which are linked by
an edge.
Let X_n be the maximal size of an independent set in G(n,a/n)
Then it is natural to believe
n^{-1} EX_n \to c(a)
since by considering isolated vertices we have a lower bound
e^{-a}> for the limit.
History. Mentioned in talks in the 1990s and posed in the 2003 postscript version of Open Problems but (for some reason) not later copied into this HTML.