The run transform

Abstract

We consider the transform from sequences to triangular arrays defined in terms of generating functions by f(x)→1−x1−xyf(x(1−x)1−xy). We establish a criterion for the transform of a nonnegative sequence to be nonnegative, and we show the transform counts certain classes of lattice paths by number of the so-called pyramid ascents and certain classes of partitions into sets of lists (blocks) by number of blocks that consist of increasing consecutive integers.