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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 5 |
| 6 | 18 |
| 7 | 74 |
| 8 | 339 |
| 9 | 1770 |
| 10 | 10915 |
| 11 | 79555 |
| 12 | 663140 |
| 13 | 6109351 |
| 14 | 61264436 |
| 15 | 669862580 |
| 16 | 8044351557 |
| 17 | 106331744724 |
| 18 | 1536980041573 |
| 19 | 24028469781765 |
| 20 | 402558463751974 |
| 21 | 7195932984364585 |
| 22 | 137204787854813174 |
| 23 | 2792969599543659326 |
| 24 | 60668198155262809815 |
[1,0,1,1,2,5,18,74,339,1770,10915,79555,663140, 6109351,61264436,669862580,8044351557, 106331744724,1536980041573,24028469781765, 402558463751974,7195932984364585, 137204787854813174,2792969599543659326, 60668198155262809815] |