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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 40 |
| 3 | 1050 |
| 4 | 42336 |
| 5 | 2328480 |
| 6 | 163088640 |
| 7 | 13913499600 |
| 8 | 1401656256000 |
| 9 | 162984589447680 |
| 10 | 21497802046156800 |
| 11 | 3172717285311974400 |
| 12 | 518147911684085760000 |
| 13 | 92790773980160256000000 |
| 14 | 18083066033253630689280000 |
| 15 | 3810158522787893903827200000 |
[1,3,40,1050,42336,2328480,163088640,13913499600, 1401656256000,162984589447680,21497802046156800, 3172717285311974400,518147911684085760000, 92790773980160256000000, 18083066033253630689280000, 3810158522787893903827200000] |