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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 24 |
| 5 | 60 |
| 6 | 3000 |
| 7 | 45570 |
| 8 | 403536 |
| 9 | 10644984 |
| 10 | 297562320 |
| 11 | 5517833310 |
| 12 | 142801022760 |
| 13 | 5076208052916 |
| 14 | 150282366476424 |
| 15 | 4713707747551530 |
| 16 | 189345734667052320 |
| 17 | 7517503455423740400 |
| 18 | 295622259241028433696 |
| 19 | 13370535071068474177974 |
| 20 | 642403497550155241197240 |
[1,0,0,6,24,60,3000,45570,403536,10644984, 297562320,5517833310,142801022760,5076208052916, 150282366476424,4713707747551530, 189345734667052320,7517503455423740400, 295622259241028433696,13370535071068474177974, 642403497550155241197240] |