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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 22 |
| 6 | 105 |
| 7 | 675 |
| 8 | 4872 |
| 9 | 40614 |
| 10 | 403704 |
| 11 | 4342080 |
| 12 | 50457000 |
| 13 | 631548456 |
| 14 | 8484089328 |
| 15 | 121882518576 |
| 16 | 1865935562400 |
| 17 | 30341974222944 |
| 18 | 522466493255424 |
| 19 | 9499883854364928 |
| 20 | 181927524046316544 |
| 21 | 3713847873452280000 |
| 22 | 80378118226450517760 |
| 23 | 1816649795206970760960 |
| 24 | 42807228653571471429120 |
[1,1,2,6,22,105,675,4872,40614,403704,4342080, 50457000,631548456,8484089328,121882518576, 1865935562400,30341974222944,522466493255424, 9499883854364928,181927524046316544, 3713847873452280000,80378118226450517760, 1816649795206970760960,42807228653571471429120] |