n | a(n) |
---|---|
0 | 1 |
1 | 1 |
2 | 4 |
3 | 20 |
4 | 116 |
5 | 756 |
6 | 5448 |
7 | 43032 |
8 | 370704 |
9 | 3472656 |
10 | 35303424 |
11 | 388786176 |
12 | 4628774016 |
13 | 59431077504 |
14 | 820503839232 |
15 | 12140411779584 |
16 | 191844739736064 |
17 | 3226219598338560 |
18 | 57540789020021760 |
19 | 1084906603389864960 |
[1,1,4,20,116,756,5448,43032,370704,3472656, 35303424,388786176,4628774016,59431077504, 820503839232,12140411779584,191844739736064, 3226219598338560,57540789020021760, 1084906603389864960] |