n | a(n) |
---|---|
1 | 1 |
2 | 4 |
3 | 12 |
4 | 40 |
5 | 140 |
6 | 816 |
7 | 5082 |
8 | 40800 |
9 | 363258 |
10 | 3632880 |
11 | 39916910 |
12 | 479052528 |
13 | 6227020956 |
14 | 87178936992 |
15 | 1307674429440 |
16 | 20922800222848 |
17 | 355687428096272 |
18 | 6402373892575992 |
19 | 121645100408832342 |
20 | 2432902011892837920 |
[1,4,12,40,140,816,5082,40800,363258,3632880, 39916910,479052528,6227020956,87178936992, 1307674429440,20922800222848,355687428096272, 6402373892575992,121645100408832342, 2432902011892837920] |