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| n | a(n) |
|---|---|
| 2 | 5 |
| 3 | 21 |
| 4 | 176 |
| 5 | 680 |
| 6 | 5808 |
| 7 | 21840 |
| 8 | 190976 |
| 9 | 708480 |
| 10 | 6310400 |
| 11 | 23220736 |
| 12 | 209756160 |
| 13 | 767676416 |
| 14 | 7010676736 |
| 15 | 25558732800 |
| 16 | 235443322880 |
| 17 | 855858053120 |
| 18 | 7939647995904 |
| 19 | 28796047982592 |
| 20 | 268690773770240 |
| 21 | 972740537352192 |
| 22 | 9120760620646400 |
[5,21,176,680,5808,21840,190976,708480,6310400, 23220736,209756160,767676416,7010676736, 25558732800,235443322880,855858053120, 7939647995904,28796047982592,268690773770240, 972740537352192,9120760620646400] |