n | a(n) |
---|---|
0 | 1 |
1 | 4 |
2 | 12 |
3 | 46 |
4 | 220 |
5 | 1268 |
6 | 8568 |
7 | 66456 |
8 | 582048 |
9 | 5681952 |
10 | 61174080 |
11 | 720089280 |
12 | 9199906560 |
13 | 126783809280 |
14 | 1874605662720 |
15 | 29601115891200 |
16 | 497155992883200 |
17 | 8849184886886400 |
18 | 166399076525875200 |
19 | 3296032301811916800 |
20 | 68596838245232640000 |
21 | 1496490349337948160000 |
[1,4,12,46,220,1268,8568,66456,582048,5681952, 61174080,720089280,9199906560,126783809280, 1874605662720,29601115891200,497155992883200, 8849184886886400,166399076525875200, 3296032301811916800,68596838245232640000, 1496490349337948160000] |