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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 24 |
| 5 | 175 |
| 6 | 1386 |
| 7 | 12397 |
| 8 | 125664 |
| 9 | 1431261 |
| 10 | 18099300 |
| 11 | 251194911 |
| 12 | 3788383248 |
| 13 | 61584927495 |
| 14 | 1072118178768 |
| 15 | 19882255276485 |
| 16 | 391068812992512 |
| 17 | 8128569896422821 |
| 18 | 177984169080865992 |
| 19 | 4094103029211918567 |
| 20 | 98692513234032009600 |
| 21 | 2487731188418039207007 |
[1,0,0,3,24,175,1386,12397,125664,1431261, 18099300,251194911,3788383248,61584927495, 1072118178768,19882255276485,391068812992512, 8128569896422821,177984169080865992, 4094103029211918567,98692513234032009600, 2487731188418039207007] |