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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 90 |
| 5 | 714 |
| 6 | 9352 |
| 7 | 16575 |
| 8 | 617139 |
| 9 | 721970 |
| 10 | 6449639 |
| 11 | 1303324906 |
| 12 | 13250660627 |
| 13 | 37151747513 |
| 14 | 211221121752 |
[1,1,4,90,714,9352,16575,617139,721970,6449639, 1303324906,13250660627,37151747513,211221121752] |