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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 122 |
| 6 | 758 |
| 7 | 5606 |
| 8 | 48378 |
| 9 | 479532 |
| 10 | 5390940 |
| 11 | 68022932 |
| 12 | 954948752 |
| 13 | 14804391270 |
| 14 | 251815549396 |
| 15 | 4673137101108 |
| 16 | 94148342547146 |
| 17 | 2050127343000170 |
| 18 | 48061939075355080 |
| 19 | 1208742383083994580 |
| 20 | 32507565146820336836 |
| 21 | 932149980847656487522 |
[1,1,2,6,24,122,758,5606,48378,479532,5390940, 68022932,954948752,14804391270,251815549396, 4673137101108,94148342547146,2050127343000170, 48061939075355080,1208742383083994580, 32507565146820336836,932149980847656487522] |