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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 116 |
| 6 | 4 |
| 7 | 632 |
| 8 | 80 |
| 9 | 8 |
| 10 | 3720 |
| 11 | 1056 |
| 12 | 240 |
| 13 | 24 |
| 14 | 23072 |
| 15 | 11680 |
| 16 | 4480 |
| 17 | 992 |
| 18 | 96 |
[1,2,6,24,116,4,632,80,8,3720,1056,240,24,23072, 11680,4480,992,96] |