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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 0 |
| 6 | 0 |
| 7 | 2520 |
| 8 | 40320 |
| 9 | 0 |
| 10 | 1209600 |
| 11 | 39916800 |
| 12 | 479001600 |
| 13 | 1556755200 |
| 14 | 79913433600 |
| 15 | 1961511552000 |
| 16 | 25107347865600 |
| 17 | 296406190080000 |
| 18 | 11204153985024000 |
| 19 | 263564384219136000 |
| 20 | 4284610758844416000 |
| 21 | 95795516571955200000 |
| 22 | 3345240261242880000000 |
[1,0,0,0,24,0,0,2520,40320,0,1209600,39916800, 479001600,1556755200,79913433600,1961511552000, 25107347865600,296406190080000,11204153985024000, 263564384219136000,4284610758844416000, 95795516571955200000,3345240261242880000000] |