is a circulating continued fraction. √2 : [1; 2, 2, 2, 2, 2, 2, …] √7 : [2; 1, 1, 1, 4, 1, 1, 1, 4, ...] (7+√13)/3: [3; 1, 1, 6, 1, 1, 1, 1, 6, 1, 1, 1, 1, 6, …] But non-quadratic irrational numbers do not circulating. ∛ 2 : [1; 3, 1, 5, 1, 1, 4, 1, 1, …] e : [2; 1, 2, 1, 1, 4, 1, 1, 6, …] And what is terminated becomes an approximation. e ≒ [2; 1, 2, 1] = 2.75