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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 12 |
| 5 | 96 |
| 6 | 480 |
| 7 | 5760 |
| 8 | 8064 |
| 9 | 645120 |
| 10 | 5806080 |
| 11 | 116121600 |
| 12 | 1277337600 |
| 13 | 6131220480 |
| 14 | 398529331200 |
| 15 | 11158821273600 |
| 16 | 167382319104000 |
| 17 | 5356234211328000 |
| 18 | 18211196318515200 |
| 19 | 3278015337332736000 |
| 20 | 62282291409321984000 |
| 21 | 146546568021934080000 |
| 22 | 52317124783830466560000 |
[1,1,1,4,12,96,480,5760,8064,645120,5806080, 116121600,1277337600,6131220480,398529331200, 11158821273600,167382319104000,5356234211328000, 18211196318515200,3278015337332736000, 62282291409321984000,146546568021934080000, 52317124783830466560000] |