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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 640 |
| 7 | 3924 |
| 8 | 28656 |
| 9 | 211984 |
| 10 | 1841052 |
| 11 | 16619224 |
| 12 | 170244216 |
| 13 | 1872923892 |
| 14 | 21777129140 |
| 15 | 280485621020 |
| 16 | 3762640368156 |
[1,2,6,24,120,640,3924,28656,211984,1841052, 16619224,170244216,1872923892,21777129140, 280485621020,3762640368156] |