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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 24 |
| 5 | 64 |
| 6 | 540 |
| 7 | 8640 |
| 8 | 34560 |
| 9 | 103680 |
| 10 | 3326400 |
| 11 | 23224320 |
| 12 | 96768000 |
| 13 | 764225280 |
| 14 | 24385536000 |
| 15 | 108391219200 |
| 16 | 1097349120000 |
| 17 | 29847896064000 |
| 18 | 1631977611264000 |
| 19 | 12384682168320000 |
| 20 | 8034351316992000 |
| 21 | 36502221127680000 |
[1,1,2,24,64,540,8640,34560,103680,3326400, 23224320,96768000,764225280,24385536000, 108391219200,1097349120000,29847896064000, 1631977611264000,12384682168320000, 8034351316992000,36502221127680000] |