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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 0 |
| 4 | 0 |
| 5 | 20 |
| 6 | 45 |
| 7 | 504 |
| 8 | 3640 |
| 9 | 33480 |
| 10 | 333585 |
| 11 | 3671360 |
| 12 | 44053416 |
| 13 | 572698620 |
| 14 | 8017774765 |
| 15 | 120266629560 |
| 16 | 1924266062160 |
| 17 | 32712523070864 |
| 18 | 588825415257345 |
| 19 | 11187682889912640 |
| 20 | 223753657798223920 |
| 21 | 4698826813762738020 |
| 22 | 103374189902780192781 |
| 23 | 2377606367763944486840 |
[1,0,0,20,45,504,3640,33480,333585,3671360, 44053416,572698620,8017774765,120266629560, 1924266062160,32712523070864,588825415257345, 11187682889912640,223753657798223920, 4698826813762738020,103374189902780192781, 2377606367763944486840] |