Catalan 数 Catn 按照这样定义:
1, 2, 3, 4, 5, 6, 7, 8, 9, 10; 1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862; 11, 12, 13, 14, 15; 16796, 58786, 208012, 742900, 2674440; 16, 17, 18, 19, 20; 9694845, 35357670, 129644790, 477638700, 1767263190; 21, 22, 23, 24, 25, 26 6564120420, 24466267020, 91482563640, 343059613650, 1289904147324, 4861946401452
A000108