Find the first three terms and the nth term of the series with the sum to n terms , , given by :

(1)

I know the first three terms . The answer given by the book for the nth term is :

My question is if that's the answer , why can't i get the first term which is 3 when i substitute n=1 into the formula .

And if it says n is greater than 1 , then there is no way to find the first term.