How can you partition n number of distinguishable objects into m number of indistinguishable blocks given that each of the blocks consists of not less than k number of objects.
(k =1 case can be explained by Stirling numbers of second kind and
k= 3 case can be used to obtain number of different ways to partition the set of vertices of a convex n-gon into polygons.)



Partitioning distinguishable objects into indistinguishable blocks
These are called "$k$-associated Stirling numbers of the 2nd kind": see <https://en.wikipedia.org/wiki/Stirling_numbers_of_the_second_kind#Associated_Stirling_numbers_of_the_second_kind>.


