Well, as presented in Tao's post, the set Ω can be either the natural numbers or the real numbers. So I'm assuming the "subsequence" is a (perhaps uncountable?)

Well, as presented in Tao's post, the set Ω can be either the natural numbers or the real numbers. So I'm assuming the "subsequence" is a (perhaps uncountable?) set of real parameters, in the latter case.