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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 20 |
| 5 | 85 |
| 6 | 534 |
| 7 | 3703 |
| 8 | 29672 |
| 9 | 266985 |
| 10 | 2669930 |
| 11 | 29369131 |
| 12 | 352429692 |
| 13 | 4581585853 |
| 14 | 64142202110 |
| 15 | 962133031455 |
| 16 | 15394128503504 |
| 17 | 261700184559313 |
| 18 | 4710603322067922 |
| 19 | 89501463119290195 |
| 20 | 1790029262385804260 |
| 21 | 37590614510101889061 |
| 22 | 826993519222241559782 |
[0,1,2,3,20,85,534,3703,29672,266985,2669930, 29369131,352429692,4581585853,64142202110, 962133031455,15394128503504,261700184559313, 4710603322067922,89501463119290195, 1790029262385804260,37590614510101889061, 826993519222241559782] |