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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 24 |
| 4 | 192 |
| 5 | 1032 |
| 6 | 5376 |
| 7 | 26688 |
| 8 | 128880 |
| 9 | 605664 |
| 10 | 2802576 |
| 11 | 12755136 |
| 12 | 57525552 |
| 13 | 256574352 |
| 14 | 1137418464 |
| 15 | 5001796944 |
| 16 | 21899428128 |
| 17 | 95296531680 |
| 18 | 413331190896 |
[0,0,24,192,1032,5376,26688,128880,605664,2802576, 12755136,57525552,256574352,1137418464,5001796944, 21899428128,95296531680,413331190896] |