A073881 a(n) = smallest number m (obviously prime) such that pi(m) = 2*pi(n).

1, 3, 7, 7, 13, 13, 19, 19, 19, 19, 29, 29, 37, 37, 37, 37, 43, 43, 53, 53, 53, 53, 61, 61, 61, 61, 61, 61, 71, 71, 79, 79, 79, 79, 79, 79, 89, 89, 89, 89, 101, 101, 107, 107, 107, 107, 113, 113, 113, 113, 113, 113, 131, 131, 131, 131, 131, 131, 139, 139, 151, 151