Question: How can I determine formulas of the sequence?

I am trying to find formula of the sequence f(n)

f(n+1) = (1+f(n))/(2*f(n)), f(1) = -7/13

I tried
restart;
rsolve({f(1) = -7/13, f(n+1) = (1+f(n))/(2*f(n))}, {f})


But I couldn't get the result. With Mathematica, I got the result.

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