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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 15 |
| 5 | 24 |
| 6 | 42 |
| 7 | 240 |
| 8 | 648 |
| 9 | 168 |
| 10 | 480 |
| 11 | 321408 |
| 12 | 4320 |
| 13 | 57120 |
| 14 | 103680 |
| 15 | 1827840 |
| 16 | 23591520 |
| 17 | 898128000 |
| 18 | 374250240 |
[1,2,8,15,24,42,240,648,168,480,321408,4320,57120, 103680,1827840,23591520,898128000,374250240] |