Random walk

Can you please help me with this question.
a) Consider the random walk on Z with transition probabilities $p_{i,i+1}$ = $p_{i,i-1}$ = 1/2 for
all i.
i) Find an expression for $p_{00}^{t}$ for all t.
ii) Use your answer to part i) to calculate $f_{00}^{t}$ for $t<=6$
Thanks