Fellowship grouping problem

Fellowship grouping problem.

We sometime need to divide our members in different cell groups, but we don't have fix number of groups each time.

If there are only one member in fellowship. We there are only 1 possible way to group them.

If there are two people, we can have 2 possible ways to group them.

For example :

  Members: Alex, Bennett

  1st way, we have 2 groups : {Group 1: Alex} and {Group 2: Bennett}.
  2nd way, we have 1 group : {Group 1: Alex and Bennett}.

  So, we have 2 possible way to group for 2 members.

Similarly, if we have 3 members, we will have 5 possible way to group people.
  For example, we have 3 groups : {Alex},{Bennett} and {Carol}.
or, we have 2 groups : {Alex, Bennett} and {Carol}
or, we have 2 groups : {Alex} and {Bennett,Carol}
or, we have 2 groups : {Bennett} and {Alex,Carol}
or, we just have one group : {Alex,Bennett,Carol}

My questions is how many way of grouping we can have if our fellowship have N people.