 This implies that the likelihood that a randomly chosen number less than formula_1 is prime is (approximately) inversely proportional to the number of digits in formula_1.It also implies that the formula_1th prime number is proportional to formula_102
and therefore that the average size of a prime gap is proportional to formula_103.A more accurate estimate for formula_89 is given by the offset logarithmic integral

An arithmetic progression is a finite or infinite sequence of numbers such that consecutive numbers in the sequence all have the same difference.