New minor minimal non-apex graphs

A graph is apex if it becomes planar after the deletion of one vertex. The family of apex graphs is closed under taking minors, so it is characterized by a finite set of forbidden minors. Determining the finite set of forbidden minors for apex graphs remains an open question. In this paper, we list all forbidden minors for apex graphs with 12 or fewer vertices and all forbidden minors for apex graphs with 26 and fewer edges. We also present graphs outside of these ranges. We show that a graph with 13 vertices and minimal degree 6 is either apex or contains a $K_6$ minor, proving J\o rgensen's conjecture for order 13.