The series starts with 2.
We multiply first term with 6 to get second term 12
Then we multiply second term with 5 to get third term 60
Then we multiply third term with 4 to get fourth term 340
Then we multiply fourth term with 3 to get fifth term 720
Then we multiply fifth term with 2 to get fifth term 1440.
Then we need to multiply with 1 and we get 1440 again.
