  Binary sequences with low autocorrelations are important in communication
engineering and in statistical mechanics as groundstates of the
Bernasconi-model. Computer searches are the main tool to construct such
sequences. Due to the exponential size $O(2^N)$ of the configuration space,
exhaustive searches are limited to short sequences. We discuss an exhaustive
search algorithm with run time characteristic $O(1.85^N)$ and apply it to
compile a table of exact groundstates of the Bernasconi-model up to $N=48$. The
data suggests $F>9$ for the optimal merit factor in the limit $N\to\infty$.
