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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 60 |
| 5 | 404 |
| 6 | 2912 |
| 7 | 21984 |
| 8 | 171600 |
| 9 | 1373680 |
| 10 | 11215776 |
| 11 | 93039648 |
| 12 | 781936896 |
| 13 | 6643741440 |
| 14 | 56973685760 |
| 15 | 492482782208 |
| 16 | 4286561051904 |
| 17 | 37536888622848 |
| 18 | 330471001126400 |
| 19 | 2923338431270400 |
| 20 | 25970490200202240 |
| 21 | 231607762146309120 |
| 22 | 2072719382680535040 |
[1,2,10,60,404,2912,21984,171600,1373680,11215776, 93039648,781936896,6643741440,56973685760, 492482782208,4286561051904,37536888622848, 330471001126400,2923338431270400, 25970490200202240,231607762146309120, 2072719382680535040] |