What is the connection between the Leiden wall poems and the Leiden wall formulas?

The wall poems have been realized by the TEGEN-BEELD Foundation, since 1992. In 2015 the physicists Sense Jan van der Molen en Ivo van Vulpen approached the foundation to realize wall formulas on the Leiden walls. So far (june 2018), six formulas have been painted on the Leiden city walls. The wall formulas can be found at muurformules.nl.