Catalan數字 

Catalan數字
0 1
1 1
2 2
3 5
4 14
5 42
6 132
7 429
8 1430
9 4862
10 16796
11 58786
12 208012
13 742900
14 2674440
15 9694845
參考資料: Martin Gardner, Time Travel and Other Mathematical Bewilderments, pp. 254-255.