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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 3 |
| 5 | 44 |
| 6 | 260 |
| 7 | 3534 |
| 8 | 40796 |
| 9 | 658440 |
| 10 | 11066184 |
| 11 | 220005840 |
| 12 | 4750650432 |
| 13 | 114430365048 |
| 14 | 2993377996440 |
| 15 | 85208541290040 |
| 16 | 2611784941760640 |
| 17 | 85941161628865344 |
| 18 | 3018822193183216320 |
| 19 | 112805065528683216192 |
| 20 | 4467115744449046110720 |
| 21 | 186900232401341222964480 |
| 22 | 8237944325702047624948224 |
[1,1,0,2,3,44,260,3534,40796,658440,11066184, 220005840,4750650432,114430365048,2993377996440, 85208541290040,2611784941760640,85941161628865344, 3018822193183216320,112805065528683216192, 4467115744449046110720,186900232401341222964480, 8237944325702047624948224] |