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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 51 |
| 4 | 561 |
| 5 | 7556 |
| 6 | 120196 |
| 7 | 2201856 |
| 8 | 45592666 |
| 9 | 1051951026 |
| 10 | 26740775306 |
| 11 | 742069051906 |
| 12 | 22310563733864 |
| 13 | 722108667742546 |
| 14 | 25024187820786357 |
| 15 | 924161461265888370 |
| 16 | 36223781285638309482 |
| 17 | 1501552062016443881514 |
[1,1,6,51,561,7556,120196,2201856,45592666, 1051951026,26740775306,742069051906, 22310563733864,722108667742546,25024187820786357, 924161461265888370,36223781285638309482, 1501552062016443881514] |