+2! + 3! 3 / 2 +2! + 3! 3 / 3 Plus + 3! + 4! 4 / 4 plus 3! + 4! + 5! 5 / 5 Plus + (n + 1)! + (n + 2)! Sum of 1 / 1
an=n/[(n-2)!+(n-1)!+n!]=1/[n(n-2)!]=(n-1)/n!=1/(n-1)!-1/n!
So: SN = 1-1 / N!
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