B h sequences

Let A be a set (finite or infinite) of natural numbers, and let a i denote a generic element of A. We say that A is a B h sequence if the sums of the form a 1 + … + a h (a 1 ≤ … ≤ a h ) are all distinct. We give an expository account of upper bounds for B h sequences. We also give a new upper bound for B 3 sequences.