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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 108 |
| 6 | 596 |
| 7 | 3674 |
| 8 | 26068 |
| 9 | 202470 |
| 10 | 1753884 |
| 11 | 16435754 |
| 12 | 168174596 |
| 13 | 1842418704 |
| 14 | 21757407158 |
| 15 | 272771715272 |
| 16 | 3649515044178 |
| 17 | 51532670206504 |
| 18 | 770442883634326 |
| 19 | 12093451621846094 |
| 20 | 199856952123506304 |
| 21 | 3452120352032161404 |
| 22 | 62471981051497913826 |
| 23 | 1177664861561125869100 |
| 24 | 23163177237781937250558 |
[1,1,2,6,24,108,596,3674,26068,202470,1753884, 16435754,168174596,1842418704,21757407158, 272771715272,3649515044178,51532670206504, 770442883634326,12093451621846094, 199856952123506304,3452120352032161404, 62471981051497913826,1177664861561125869100, 23163177237781937250558] |