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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 58 |
| 4 | 920 |
| 5 | 21176 |
| 6 | 654960 |
| 7 | 26114768 |
| 8 | 1298070912 |
| 9 | 78359732608 |
| 10 | 5630565514496 |
| 11 | 473796572027648 |
| 12 | 46060380961356800 |
| 13 | 5114737212582603776 |
| 14 | 642502387594286036992 |
| 15 | 90542358999393528670208 |
| 16 | 14209873001490130067095552 |
| 17 | 2467784343879850163370295296 |
| 18 | 471558856613839054976849608704 |
[1,1,6,58,920,21176,654960,26114768,1298070912, 78359732608,5630565514496,473796572027648, 46060380961356800,5114737212582603776, 642502387594286036992,90542358999393528670208, 14209873001490130067095552, 2467784343879850163370295296, 471558856613839054976849608704] |