| n | a(n) |
|---|---|
| 2 | 12 |
| 3 | 105 |
| 4 | 831 |
| 5 | 6648 |
| 6 | 53545 |
| 7 | 434458 |
| 8 | 3548871 |
| 9 | 29166324 |
| 10 | 241006333 |
| 11 | 2001145585 |
| 12 | 16688238416 |
| 13 | 139711675493 |
| 14 | 1173762075101 |
| 15 | 9892582661593 |
| 16 | 83617537623039 |
| 17 | 708654873428000 |
| 18 | 6020421349942965 |
| 19 | 51261344063828713 |
| 20 | 437370998284452284 |
| 21 | 3738875265960650016 |
[12,105,831,6648,53545,434458,3548871,29166324, 241006333,2001145585,16688238416,139711675493, 1173762075101,9892582661593,83617537623039, 708654873428000,6020421349942965, 51261344063828713,437370998284452284, 3738875265960650016] |