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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 120 |
| 5 | 1600 |
| 6 | 28500 |
| 7 | 621138 |
| 8 | 16017792 |
| 9 | 480474720 |
| 10 | 16390969920 |
| 11 | 626786792280 |
| 12 | 26584872779520 |
| 13 | 1238524175509608 |
| 14 | 62873918454756864 |
| 15 | 3455537675553482400 |
| 16 | 204449393824639488000 |
| 17 | 12958008875933613962880 |
[1,1,2,12,120,1600,28500,621138,16017792, 480474720,16390969920,626786792280,26584872779520, 1238524175509608,62873918454756864, 3455537675553482400,204449393824639488000, 12958008875933613962880] |