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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 11 |
| 5 | 55 |
| 6 | 322 |
| 7 | 2114 |
| 8 | 15556 |
| 9 | 127005 |
| 10 | 1135374 |
| 11 | 11011220 |
| 12 | 115080825 |
| 13 | 1288589757 |
| 14 | 15379512670 |
| 15 | 194796087841 |
| 16 | 2608470709562 |
| 17 | 36805935282625 |
| 18 | 545626818921885 |
| 19 | 8475730766054047 |
| 20 | 137637670315066835 |
| 21 | 2331584745107027528 |
| 22 | 41122505417366272200 |
[1,0,1,3,11,55,322,2114,15556,127005,1135374, 11011220,115080825,1288589757,15379512670, 194796087841,2608470709562,36805935282625, 545626818921885,8475730766054047, 137637670315066835,2331584745107027528, 41122505417366272200] |