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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 94 |
| 6 | 450 |
| 7 | 2366 |
| 8 | 13450 |
| 9 | 81802 |
| 10 | 527826 |
| 11 | 3590294 |
| 12 | 25609782 |
| 13 | 190753502 |
| 14 | 1478339866 |
| 15 | 11884997478 |
| 16 | 98859026322 |
| 17 | 848881803218 |
| 18 | 7509881820930 |
| 19 | 68330806392070 |
| 20 | 638444805545622 |
| 21 | 6117166765086366 |
| 22 | 60028033370994386 |
[1,1,2,6,22,94,450,2366,13450,81802,527826, 3590294,25609782,190753502,1478339866,11884997478, 98859026322,848881803218,7509881820930, 68330806392070,638444805545622,6117166765086366, 60028033370994386] |