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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 120 |
| 5 | 1800 |
| 6 | 37440 |
| 7 | 1023120 |
| 8 | 35360640 |
| 9 | 1502323200 |
| 10 | 76738233600 |
| 11 | 4629350880000 |
| 12 | 325036115712000 |
| 13 | 26238156161817600 |
| 14 | 2409994778846054400 |
| 15 | 249634150247978496000 |
| 16 | 28935351060849192960000 |
| 17 | 3727654806346921562112000 |
| 18 | 530531863561703729037312000 |
[1,1,2,12,120,1800,37440,1023120,35360640, 1502323200,76738233600,4629350880000, 325036115712000,26238156161817600, 2409994778846054400,249634150247978496000, 28935351060849192960000,3727654806346921562112000, 530531863561703729037312000] |