| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 132 |
| 5 | 2040 |
| 6 | 40350 |
| 7 | 974400 |
| 8 | 27805736 |
| 9 | 915505920 |
| 10 | 34160797530 |
| 11 | 1424581678080 |
| 12 | 65660547312492 |
| 13 | 3314551571595264 |
| 14 | 181866769617012662 |
| 15 | 10777121944589844480 |
| 16 | 685937077729538151120 |
| 17 | 46668919680893409361920 |
| 18 | 3380042082757952844150066 |
| 19 | 259638732115410022642483200 |
[1,2,12,132,2040,40350,974400,27805736,915505920, 34160797530,1424581678080,65660547312492, 3314551571595264,181866769617012662, 10777121944589844480,685937077729538151120, 46668919680893409361920,3380042082757952844150066, 259638732115410022642483200] |