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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 720 |
| 3 | 103680 |
| 4 | 1474560 |
| 5 | 37440000 |
| 6 | 74649600 |
| 7 | 1659571200 |
| 8 | 3019898880 |
| 9 | 18366600960 |
| 10 | 26956800000 |
| 11 | 257213088000 |
| 12 | 152882380800 |
| 13 | 1644455554560 |
| 14 | 1194891264000 |
| 15 | 3881779200000 |
| 16 | 6184752906240 |
| 17 | 32143905423360 |
| 18 | 13223952691200 |
| 19 | 110052644025600 |
| 20 | 55207526400000 |
| 21 | 172064342016000 |
| 22 | 185193423360000 |
[1,720,103680,1474560,37440000,74649600, 1659571200,3019898880,18366600960,26956800000, 257213088000,152882380800,1644455554560, 1194891264000,3881779200000,6184752906240, 32143905423360,13223952691200,110052644025600, 55207526400000,172064342016000,185193423360000] |