On a necessary conditon for the Erdos-Rnyi law of large numbers

For a sequence (X),1,2,2... of independent, identically distributed random variables with existing moment-generating function )(t) E exp(tX1) in some nondegenerate interval, Erdos and Renyi (1970) studied the maximum D (N, K) of the N K + 1 sample means K I(Sn+ K -Se), 0 n 0, andputting SO = 0, S, = .1_ 1Xi, and D(N,K)= max Sn+K n (1 < K N),