alan turing algorithmic probability algorithmically random sequence andrey kolmogorov axiom blum axioms claude shannon computer science data structure distribution ensemble epistemology gregory chaitin halting problem information theory integer intuition invariance theorem kolmogorov complexity lebesgue measure leonid levin limit of a sequence minimum description length minimum message length nondeterminism normal number programming language pseudorandom ensemble pseudorandom generator ray solomonoff real number sequence theory of computation uniform ensemble