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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 25 |
| 4 | 218 |
| 5 | 2451 |
| 6 | 33112 |
| 7 | 516727 |
| 8 | 9117180 |
| 9 | 179330905 |
| 10 | 3890434256 |
| 11 | 92271385449 |
| 12 | 2374775505016 |
| 13 | 65900749176835 |
| 14 | 1961009596461840 |
| 15 | 62275489622799751 |
| 16 | 2101798757669917328 |
| 17 | 75111617959762807473 |
[1,1,4,25,218,2451,33112,516727,9117180,179330905, 3890434256,92271385449,2374775505016, 65900749176835,1961009596461840,62275489622799751, 2101798757669917328,75111617959762807473] |