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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 32 |
| 5 | 176 |
| 6 | 952 |
| 7 | 5302 |
| 8 | 29960 |
| 9 | 172536 |
| 10 | 1007575 |
| 11 | 5959656 |
| 12 | 35622384 |
| 13 | 214875104 |
| 14 | 1306303424 |
| 15 | 7995896502 |
| 16 | 49236826080 |
| 17 | 304799714960 |
| 18 | 1895785216039 |
| 19 | 11841367945110 |
| 20 | 74245791718824 |
| 21 | 467136323951040 |
| 22 | 2948374926743584 |
[0,0,1,6,32,176,952,5302,29960,172536,1007575, 5959656,35622384,214875104,1306303424,7995896502, 49236826080,304799714960,1895785216039, 11841367945110,74245791718824,467136323951040, 2948374926743584] |