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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 90 |
| 5 | 6720 |
| 6 | 36960 |
| 7 | 11642400 |
| 8 | 283046400 |
| 9 | 2412984420000 |
| 10 | 1140422816332800 |
| 11 | 1226781977195174400 |
| 12 | 1863152400854384640000 |
| 13 | 5988092802221559085056000 |
| 14 | 112886540292742916603904000 |
| 15 | 158983195607776600998537600000000 |
[1,2,6,90,6720,36960,11642400,283046400, 2412984420000,1140422816332800, 1226781977195174400,1863152400854384640000, 5988092802221559085056000, 112886540292742916603904000, 158983195607776600998537600000000] |