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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 29 |
| 7 | 178 |
| 8 | 1270 |
| 9 | 10366 |
| 10 | 95020 |
| 11 | 966033 |
| 12 | 10787363 |
| 13 | 131246246 |
| 14 | 1728075563 |
| 15 | 24481070470 |
| 16 | 371296235456 |
| 17 | 6002622473193 |
| 18 | 103045019123133 |
| 19 | 1871984514070245 |
| 20 | 35879703186346360 |
| 21 | 723574014257984911 |
[1,1,1,1,2,6,29,178,1270,10366,95020,966033, 10787363,131246246,1728075563,24481070470, 371296235456,6002622473193,103045019123133, 1871984514070245,35879703186346360, 723574014257984911] |