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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 25 |
| 5 | 91 |
| 6 | 444 |
| 7 | 2920 |
| 8 | 25996 |
| 9 | 314752 |
| 10 | 5201874 |
| 11 | 117719942 |
| 12 | 3658433597 |
| 13 | 156505343943 |
| 14 | 9234365056453 |
| 15 | 752841451059559 |
| 16 | 84938741035295776 |
| 17 | 13279814559055121447 |
| 18 | 2880581923860441220144 |
| 19 | 867855593621657824023139 |
[1,2,4,9,25,91,444,2920,25996,314752,5201874, 117719942,3658433597,156505343943,9234365056453, 752841451059559,84938741035295776, 13279814559055121447,2880581923860441220144, 867855593621657824023139] |