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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 75 |
| 5 | 541 |
| 6 | 4683 |
| 7 | 47293 |
| 8 | 545835 |
| 9 | 7087261 |
| 10 | 102247563 |
| 11 | 1520385010 |
| 12 | 23523325304 |
| 13 | 380789137336 |
| 14 | 6467270373536 |
| 15 | 115360990236256 |
| 16 | 2161133759447744 |
| 17 | 42490485277902688 |
| 18 | 875847933546165968 |
| 19 | 18903517993567133752 |
| 20 | 426618313415065361204 |
| 21 | 10043227358229156346032 |
[1,1,3,13,75,541,4683,47293,545835,7087261, 102247563,1520385010,23523325304,380789137336, 6467270373536,115360990236256,2161133759447744, 42490485277902688,875847933546165968, 18903517993567133752,426618313415065361204, 10043227358229156346032] |