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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 118 |
| 6 | 644 |
| 7 | 3622 |
| 8 | 20366 |
| 9 | 113686 |
| 10 | 630464 |
| 11 | 3481084 |
| 12 | 19171838 |
| 13 | 105444400 |
| 14 | 579547826 |
| 15 | 3184321642 |
| 16 | 17493771830 |
| 17 | 96100287256 |
| 18 | 527905628552 |
| 19 | 2899911094078 |
| 20 | 15929870658308 |
| 21 | 87506389326742 |
| 22 | 480692570563526 |
| 23 | 2640554790693958 |
| 24 | 14505177373598504 |
[1,1,2,6,24,118,644,3622,20366,113686,630464, 3481084,19171838,105444400,579547826,3184321642, 17493771830,96100287256,527905628552, 2899911094078,15929870658308,87506389326742, 480692570563526,2640554790693958, 14505177373598504] |