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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 30 |
| 6 | 117 |
| 7 | 512 |
| 8 | 2597 |
| 9 | 14892 |
| 10 | 99034 |
| 11 | 721350 |
| 12 | 5909324 |
| 13 | 52578654 |
| 14 | 516148082 |
| 15 | 5422071091 |
| 16 | 61889692290 |
| 17 | 749456672155 |
[0,0,1,3,9,30,117,512,2597,14892,99034,721350, 5909324,52578654,516148082,5422071091,61889692290, 749456672155] |