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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 10 |
| 5 | 24 |
| 6 | 72 |
| 7 | 168 |
| 8 | 664 |
| 9 | 1632 |
| 10 | 5376 |
| 11 | 13152 |
| 12 | 47968 |
| 13 | 119936 |
| 14 | 406400 |
| 15 | 1017984 |
| 16 | 3585408 |
| 17 | 9082368 |
| 18 | 30987264 |
| 19 | 78761472 |
| 20 | 272565760 |
| 21 | 697493504 |
| 22 | 2378450944 |
| 23 | 6107523072 |
| 24 | 20921604096 |
| 25 | 53972262912 |
| 26 | 183506403328 |
| 27 | 474876108800 |
[1,1,2,10,24,72,168,664,1632,5376,13152,47968, 119936,406400,1017984,3585408,9082368,30987264, 78761472,272565760,697493504,2378450944, 6107523072,20921604096,53972262912,183506403328, 474876108800] |