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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 96 |
| 5 | 1120 |
| 6 | 16260 |
| 7 | 290640 |
| 8 | 6108480 |
| 9 | 148353408 |
| 10 | 4081855680 |
| 11 | 125613124560 |
| 12 | 4274457264000 |
| 13 | 159409774592640 |
| 14 | 6465790781049600 |
| 15 | 283412493387223200 |
| 16 | 13350812617606464000 |
| 17 | 672683432660494295040 |
| 18 | 36100038651180773068800 |
[1,1,2,12,96,1120,16260,290640,6108480,148353408, 4081855680,125613124560,4274457264000, 159409774592640,6465790781049600, 283412493387223200,13350812617606464000, 672683432660494295040,36100038651180773068800] |