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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 40320 |
| 10 | 4032000 |
| 11 | 266112000 |
| 12 | 15008716800 |
| 13 | 794060467200 |
| 14 | 41179634496000 |
| 15 | 2142915046272000 |
| 16 | 113401428940800000 |
| 17 | 6150985123214131200 |
| 18 | 343578020565722342400 |
| 19 | 19818131438503157760000 |
| 20 | 1182304993642509574656000 |
| 21 | 73005714001076187082752000 |
[0,0,0,0,0,0,0,0,0,40320,4032000,266112000, 15008716800,794060467200,41179634496000, 2142915046272000,113401428940800000, 6150985123214131200,343578020565722342400, 19818131438503157760000,1182304993642509574656000, 73005714001076187082752000] |