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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 64 |
| 5 | 620 |
| 6 | 7626 |
| 7 | 113792 |
| 8 | 1997192 |
| 9 | 40316544 |
| 10 | 920271840 |
| 11 | 23438308872 |
| 12 | 658947505272 |
| 13 | 20270099889624 |
| 14 | 677226678369528 |
| 15 | 24420959694718680 |
| 16 | 945370712175873216 |
| 17 | 39103903755819561984 |
| 18 | 1721215383181421110848 |
| 19 | 80329148928437231089152 |
[1,1,2,9,64,620,7626,113792,1997192,40316544, 920271840,23438308872,658947505272,20270099889624, 677226678369528,24420959694718680, 945370712175873216,39103903755819561984, 1721215383181421110848,80329148928437231089152] |