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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 240 |
| 4 | 3060 |
| 5 | 19584 |
| 6 | 77760 |
| 7 | 249120 |
| 8 | 774180 |
| 9 | 2110720 |
| 10 | 4621824 |
| 11 | 9294480 |
| 12 | 19873920 |
| 13 | 40049280 |
| 14 | 68181120 |
| 15 | 110984160 |
| 16 | 198425700 |
| 17 | 342524160 |
| 18 | 509271040 |
| 19 | 735758640 |
| 20 | 1183095144 |
[1,0,0,240,3060,19584,77760,249120,774180,2110720, 4621824,9294480,19873920,40049280,68181120, 110984160,198425700,342524160,509271040,735758640, 1183095144] |