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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 48 |
| 3 | 1704 |
| 4 | 71490 |
| 5 | 3291780 |
| 6 | 160844160 |
| 7 | 8189867280 |
| 8 | 429832053840 |
| 9 | 23088359467040 |
| 10 | 1263134996327680 |
| 11 | 70138971602098560 |
| 12 | 3942799810867610280 |
| 13 | 223942062435751452240 |
| 14 | 12831882367225056387840 |
| 15 | 740872398293620831990080 |
[1,2,48,1704,71490,3291780,160844160,8189867280, 429832053840,23088359467040,1263134996327680, 70138971602098560,3942799810867610280, 223942062435751452240,12831882367225056387840, 740872398293620831990080] |