Bell number and Equivalence Relations

Sometimes in Exam, we are given a Set and then ask us to find the number of equivalence relations. for this, we use the bell Number.


let A ={1,2,3,4} .What is total number of Eqivalence relations? 


Total number of elements in Set A= 4

So the total number of equivalence relation=15


For more bell numbers, Please refer to the given link.