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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 18 |
| 3 | 144 |
| 4 | 0 |
| 5 | -28200 |
| 6 | -814968 |
| 7 | -15203328 |
| 8 | 0 |
| 9 | 16696909080 |
| 10 | 893794451000 |
| 11 | 25789252433472 |
| 12 | 0 |
| 13 | -54804262577596532 |
| 14 | -4044941639317807200 |
| 15 | -161017938434267136000 |
| 16 | 0 |
| 17 | 621130358284578576358416 |
| 18 | 59512584052525004199214632 |
| 19 | 3008072527724272784969384000 |
| 20 | 0 |
[1,18,144,0,-28200,-814968,-15203328,0, 16696909080,893794451000,25789252433472,0, -54804262577596532,-4044941639317807200, -161017938434267136000,0,621130358284578576358416, 59512584052525004199214632, 3008072527724272784969384000,0] |