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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 1 |
| 3 | 6 |
| 4 | 24 |
| 5 | 1 |
| 6 | 180 |
| 7 | 1008 |
| 8 | 1 |
| 9 | 12960 |
| 10 | 90720 |
| 11 | 1 |
| 12 | 1710720 |
| 13 | 14152320 |
| 14 | 1 |
| 15 | 359251200 |
| 16 | 3396556800 |
| 17 | 1 |
| 18 | 109930867200 |
| 19 | 1161622425600 |
| 20 | 1 |
| 21 | 46170964224000 |
| 22 | 536669560627200 |
| 23 | 1 |
| 24 | 25486372251648000 |
| 25 | 322001736376320000 |
| 26 | 1 |
| 27 | 17891433320656896000 |
[1,2,1,6,24,1,180,1008,1,12960,90720,1,1710720, 14152320,1,359251200,3396556800,1,109930867200, 1161622425600,1,46170964224000,536669560627200,1, 25486372251648000,322001736376320000,1, 17891433320656896000] |