Feedback Vertex Number Of Sierpi(?)ski-type Graphs

The feedback vertex number??G?of a graph G is the minimum number of vertices that can be deleted from G such that the resultant graph does not contain a cycle.We show that??S_pⁿ?=p^n-1?p-2?for the Sierpi???ski graph S_pⁿwith p?2 and n?1.The generalized Sierpi???ski triangle graph?S_pⁿis obtained by contracting all non-clique edges from the Sierpi???ski graph S_pⁿ⁺¹.We prove that???S₃ⁿ?=₂³ⁿ⁺¹=₃^|V??S3n?|,and give an upper bound for???S_pⁿ?for the case when p?4.