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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 8 |
| 5 | 24 |
| 6 | 184 |
| 7 | 1000 |
| 8 | 8448 |
| 9 | 66752 |
| 10 | 670976 |
| 11 | 6771456 |
| 12 | 80540800 |
| 13 | 981684352 |
| 14 | 13555365888 |
| 15 | 193136762624 |
| 16 | 3042586824704 |
| 17 | 49558509465600 |
| 18 | 877951349198848 |
| 19 | 16081833643651072 |
| 20 | 316609129672114176 |
| 21 | 6439690754082062336 |
| 22 | 139521103623589068800 |
[1,1,0,2,8,24,184,1000,8448,66752,670976,6771456, 80540800,981684352,13555365888,193136762624, 3042586824704,49558509465600,877951349198848, 16081833643651072,316609129672114176, 6439690754082062336,139521103623589068800] |