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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 140 |
| 4 | 5544 |
| 5 | 622908 |
| 6 | 198846076 |
| 7 | 180473355920 |
| 8 | 465904151957920 |
| 9 | 3422048076740462480 |
| 10 | 71525763221287897903500 |
| 11 | 4254840960508487045451825000 |
| 12 | 720428791920558617462950575000000 |
| 13 | 347230535542092373572967034254050000000 |
[1,2,10,140,5544,622908,198846076,180473355920, 465904151957920,3422048076740462480, 71525763221287897903500, 4254840960508487045451825000, 720428791920558617462950575000000, 347230535542092373572967034254050000000] |