| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | 1800 |
| 7 | 16800 |
| 8 | 126000 |
| 9 | 834120 |
| 10 | 5103000 |
| 11 | 29607600 |
| 12 | 165528000 |
| 13 | 901020120 |
| 14 | 4809004200 |
| 15 | 25292030400 |
| 16 | 131542866000 |
| 17 | 678330198120 |
| 18 | 3474971465400 |
| 19 | 17710714165200 |
| 20 | 89904730860000 |
| 21 | 454951508208120 |
| 22 | 2296538629446600 |
| 23 | 11570026582092000 |
| 24 | 58200094019430000 |
[1,0,0,0,0,120,1800,16800,126000,834120,5103000, 29607600,165528000,901020120,4809004200, 25292030400,131542866000,678330198120, 3474971465400,17710714165200,89904730860000, 454951508208120,2296538629446600, 11570026582092000,58200094019430000] |