let Xn , n= 1, 2, . . . . . be a sequence of r.v st

p(Xn = a) = 1 - (1/n), a in R

p(Xn = n^k) = 1/n k>1 , k fixed

show Xn is consitent a consistant estimator for a.

i.e show for all e>0 p(|Xn - a|>= e) tends to 0 as n tends to infinity

any idears

thanks for you help