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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 96 |
| 5 | 480 |
| 6 | 5760 |
| 7 | 40320 |
| 8 | 645120 |
| 9 | 5806080 |
| 10 | 116121600 |
| 11 | 1277337600 |
| 12 | 30656102400 |
| 13 | 398529331200 |
| 14 | 11158821273600 |
| 15 | 167382319104000 |
| 16 | 5356234211328000 |
| 17 | 91055981592576000 |
| 18 | 3278015337332736000 |
| 19 | 62282291409321984000 |
| 20 | 2491291656372879360000 |
[1,1,4,12,96,480,5760,40320,645120,5806080, 116121600,1277337600,30656102400,398529331200, 11158821273600,167382319104000,5356234211328000, 91055981592576000,3278015337332736000, 62282291409321984000,2491291656372879360000] |