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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 0 |
| 4 | 3 |
| 5 | 7 |
| 6 | 0 |
| 7 | 6 |
| 8 | 60 |
| 9 | 90 |
| 10 | 0 |
| 11 | 10 |
| 12 | 310 |
| 13 | 1505 |
| 14 | 1701 |
| 15 | 0 |
| 16 | 15 |
| 17 | 1260 |
| 18 | 14490 |
| 19 | 46620 |
| 20 | 42525 |
| 21 | 0 |
| 22 | 21 |
| 23 | 4445 |
| 24 | 105875 |
| 25 | 716205 |
| 26 | 1727110 |
| 27 | 1323652 |
| 28 | 0 |
| 29 | 28 |
| 30 | 14280 |
| 31 | 653100 |
| 32 | 8162000 |
| 33 | 38623200 |
[1,0,1,0,3,7,0,6,60,90,0,10,310,1505,1701,0,15, 1260,14490,46620,42525,0,21,4445,105875,716205, 1727110,1323652,0,28,14280,653100,8162000, 38623200] |