How many n-element semilattices there are?


For example, for n-element partially ordered set we can figured out, that there are $2^{n\*(n-1)}$ possible sets.


And can I find all possible n-element semilattices? Or maybe there are some useful rule to generate all that kind of sets? [I'm trying do something](https://stackoverflow.com/questions/4994087/prolog-sets-problem-stack-overflow), but have nothing at all with memory problems



Semilattices with n elements
By adding a top element to a (meet) semilattice we get a lattice. Hence the number of $n$-element semilattices is the number of $(n+1)$-element lattices. This number is treated in 
A006966 of Sloane.


