| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 120 |
| 3 | 4495 |
| 4 | 270725 |
| 5 | 24040016 |
| 6 | 2967205528 |
| 7 | 487444845680 |
| 8 | 103073959989495 |
| 9 | 27319423696620550 |
| 10 | 8881600973913295056 |
| 11 | 3478625214672347911080 |
| 12 | 1616770762998304775695925 |
| 13 | 880246034121663208464847200 |
[1,6,120,4495,270725,24040016,2967205528, 487444845680,103073959989495,27319423696620550, 8881600973913295056,3478625214672347911080, 1616770762998304775695925, 880246034121663208464847200] |