$1.$ Dice roll

On rolling a single die, we get six distinct outcomes $(1,2,3,4,5,6).$ On rolling two dice, we get $21$ distinct outcomes $((1,1),(2,3),(4,6),...).$

Note that getting $(2,3),$ for example, is considered same as getting $(3,2).$

Write a program to print the number of distinct outcomes when $"$n$"$ dice are rolled.