A024836 a(n) = least m such that if r and s in {1/1, 1/4, 1/7, ..., 1/(3n-2)} satisfy r > s, then r > k/m > (k-1)/m > s for some integer k.

3, 13, 29, 51, 92, 131, 193, 248, 331, 401, 505, 590, 715, 852, 963, 1121, 1291, 1427, 1618, 1821, 1981, 2205, 2441, 2625, 2882, 3151, 3361, 3651, 3953, 4267, 4511, 4846, 5193, 5552, 5829, 6209, 6601, 7005, 7315, 7740, 8177, 8626, 9087, 9441, 9923, 10417, 10923, 11441