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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 10 |
| 6 | 41 |
| 7 | 260 |
| 8 | 1552 |
| 9 | 12818 |
| 10 | 101280 |
| 11 | 1021908 |
| 12 | 10154064 |
| 13 | 121656672 |
| 14 | 1447205472 |
| 15 | 20215013184 |
| 16 | 280271024640 |
| 17 | 4457067906240 |
| 18 | 70826580095040 |
| 19 | 1264147627392000 |
| 20 | 22588177271650560 |
| 21 | 448332829478760960 |
| 22 | 8899910723677639680 |
| 23 | 194096853444946636800 |
[1,0,0,1,2,10,41,260,1552,12818,101280,1021908, 10154064,121656672,1447205472,20215013184, 280271024640,4457067906240,70826580095040, 1264147627392000,22588177271650560, 448332829478760960,8899910723677639680, 194096853444946636800] |