Ramanujan prime

Ramanujan primes are the integers R_n that are the smallest to satisfy the condition π(x) - π(x/2) ≥ n, for all x ≥ R_n. In other words, there are at least n primes between x/2 and x, whenever x is greater than or equal to R_n. The sequence begins 2, 11, 17, 29, 41, ....