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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 24 |
| 5 | 150 |
| 6 | 720 |
| 7 | 1560 |
| 8 | 87360 |
| 9 | 1670760 |
| 10 | 20420400 |
| 11 | 1999157160 |
| 12 | 13085392320 |
| 13 | 3302971111440 |
| 14 | 103154328557280 |
| 15 | 1348374437570160 |
| 16 | 67598505136850688 |
| 17 | 114701988497522458032 |
| 18 | 2307534121538392979232 |
| 19 | 10183789060049355548733936 |
[1,1,6,24,150,720,1560,87360,1670760,20420400, 1999157160,13085392320,3302971111440, 103154328557280,1348374437570160, 67598505136850688,114701988497522458032, 2307534121538392979232,10183789060049355548733936] |