Abstract.
Let $\Omega$ be the basis consisting of a negation and logical `and' and `or' operations over any number of inputs. Every Boolean function of $n$ variables can be realised by a Boolean circuit over $\Omega$ using at most $2.122\cdot 2^{n/2}+n+1$ gates ($2\cdot 2^{n/2}+n+1$ for even $n$). We also show that almost all Boolean functions have circuit complexity at least $1.914\cdot 2^{n/2}-4n$.
Keywords: boolean functions, computational complexity
Bibtex entry:
@Article{Dan96, author = "Vlado Dan{\v c}{\'\i}k", title = "Complexity of Boolean functions over bases with unbounded fan-in gates", journal = "Information Processing Letters", year = "1996", number = "1", volume = "57", pages = "31-34" }