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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 55 |
| 2 | 1260 |
| 3 | 27715 |
| 4 | 608520 |
| 5 | 13359775 |
| 6 | 293306580 |
| 7 | 6439385035 |
| 8 | 141373164240 |
| 9 | 3103770228295 |
| 10 | 68141571858300 |
| 11 | 1496010810654355 |
| 12 | 32844096262537560 |
| 13 | 721074106965172015 |
| 14 | 15830786256971246820 |
| 15 | 347556223546402258075 |
| 16 | 7630406131763878430880 |
| 17 | 167521378675258923221335 |
[0,55,1260,27715,608520,13359775,293306580, 6439385035,141373164240,3103770228295, 68141571858300,1496010810654355,32844096262537560, 721074106965172015,15830786256971246820, 347556223546402258075,7630406131763878430880, 167521378675258923221335] |