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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 0 |
| 5 | 44 |
| 6 | 304 |
| 7 | 2568 |
| 8 | 26704 |
| 9 | 200240 |
| 10 | 1931616 |
| 11 | 20849696 |
| 12 | 246556672 |
| 13 | 3300906816 |
| 14 | 46382446720 |
| 15 | 695413794944 |
| 16 | 11120648673024 |
| 17 | 188600719094528 |
| 18 | 3394592207824384 |
| 19 | 64513420630110720 |
| 20 | 1290420198709682176 |
| 21 | 27102196040419214336 |
| 22 | 596237419436696543232 |
| 23 | 13713106494042086045696 |
[1,1,2,6,0,44,304,2568,26704,200240,1931616, 20849696,246556672,3300906816,46382446720, 695413794944,11120648673024,188600719094528, 3394592207824384,64513420630110720, 1290420198709682176,27102196040419214336, 596237419436696543232,13713106494042086045696] |