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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 144 |
| 5 | 2760 |
| 6 | 74880 |
| 7 | 2676240 |
| 8 | 120234240 |
| 9 | 6571393920 |
| 10 | 426547296000 |
| 11 | 32283270835200 |
| 12 | 2808028566604800 |
| 13 | 277433852555059200 |
| 14 | 30836115140589158400 |
| 15 | 3824551325912308992000 |
| 16 | 525674251444773150720000 |
| 17 | 79591811594194480508928000 |
| 18 | 13205626859810397006618624000 |
[1,2,12,144,2760,74880,2676240,120234240, 6571393920,426547296000,32283270835200, 2808028566604800,277433852555059200, 30836115140589158400,3824551325912308992000, 525674251444773150720000, 79591811594194480508928000, 13205626859810397006618624000] |