2 papers
math.CO2007
Harmonic ultrafilters
Rudi Hirschfeld
A set of natural numbers will be called \emph{harmonic} if the reciprocals of its elements form a divergent series. An ultrafilter of the natural numbers will he called \emph{harmo…
math.CO2007
On a Generalization of the van der Waerden Theorem
Rudi Hirschfeld
For a given length and a given degree and an arbitrary partition of the positive integers, there always is a cell containing a polynomial progression of that length and that degree…