The Cameron–Erdős conjecture was proved independently by Ben Green (*The Cameron-Erdos Conjecture*) and Alexander Sapozhenko (*The Cameron-Erdős conjecture*).

Let $s(n)$ be the number of sum-free subsets of the set of integers $\{1,2,\dotsc,n\}$. They showed that ${ s(n) / 2^{n/2} } \to C_O \text{ or } C_E$, for constants $C_O$ and $C_E$, as $n \to \infty$ through odd or even values respectively.

I would like to know what are the best known bounds for the constants $C_O$ and $C_E$?

My motivation is that I considered the conjecture in the mid-1990s and tried to determine some good lower bounds for the constants on the condition that the limits existed, of course. I have a vague recollection that Cameron and Erdős had some lower bounds in the region of 5 or 6, but I no longer have their relevant papers handy to verify this.

Looking at the sequence A007865 in the OEIS, it would seem that $C_E$ is in the region of 13.4 and that $C_O$ is in the region of 14.4. If one calculates $s(n)/2^{n/2}$ for even $n$, it rises steadily from $n=0$ to $n=36$ then interestingly appears to oscillate about its limit. The sequence for odd $n$, from $n=39$ onwards, possibly does the same. It would be interesting to have some more terms.

Anyway, any information that you have on the actual values of these constants would be greatly appreciated.