  Let STS(n) denote the number of Steiner triple systems on n vertices, and let
F(n) denote the number of 1-factorizations of the complete graph on n vertices.
We prove the following upper bound.
  STS(n) <= ((1 + o(1)) (n/e^2))^(n^2/6)
  F(n) <= ((1 + o(1)) (n/e^2))^(n^2/2)
  We conjecture that the bound is sharp. Our main tool is the entropy method.
