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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 0 |
| 4 | 12 |
| 5 | 0 |
| 6 | 0 |
| 7 | 840 |
| 8 | 0 |
| 9 | 0 |
| 10 | 50400 |
| 11 | 831600 |
| 12 | 0 |
| 13 | 0 |
| 14 | 302702400 |
| 15 | 1135134000 |
| 16 | 14529715200 |
| 17 | 0 |
| 18 | 2315673360000 |
| 19 | 15545887156800 |
| 20 | 140792940288000 |
| 21 | 443497761907200 |
| 22 | 28006062372288000 |
| 23 | 623360743125120000 |
[1,2,0,12,0,0,840,0,0,50400,831600,0,0,302702400, 1135134000,14529715200,0,2315673360000, 15545887156800,140792940288000,443497761907200, 28006062372288000,623360743125120000] |