



 
Hi Penny, If n is a positive integer then the notation n! (n factorial) is used to designate n × (n2) × (n3) × … × 2 × 1, so for example 3! = 3 × 2 × 1 = 6. This definition is extended to the case than n = 0 by defining 0! = 1. I am not sure if the sequence is to start with n = 1 or n = 0 but I expect it's with n = 1. Thus the first five terms will come from n = 1, 2, 3, 4 and 5.
I hope this helps,  


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