| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 16 |
| 3 | 240 |
| 4 | 4466 |
| 5 | 89630 |
| 6 | 1856100 |
| 7 | 39162020 |
| 8 | 840122330 |
| 9 | 18350758538 |
| 10 | 409124396540 |
| 11 | 9333564282142 |
| 12 | 218396645933584 |
| 13 | 5252293916506694 |
[2,16,240,4466,89630,1856100,39162020,840122330, 18350758538,409124396540,9333564282142, 218396645933584,5252293916506694] |