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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 16 |
| 4 | 67 |
| 5 | 404 |
| 6 | 3904 |
| 7 | 64840 |
| 8 | 1930842 |
| 9 | 104698904 |
| 10 | 10401039400 |
| 11 | 1900637187280 |
| 12 | 641429385018832 |
| 13 | 401454435464761376 |
| 14 | 467919402404052870944 |
| 15 | 1019758699013228238271040 |
| 16 | 4171161230867751509749228304 |
[1,2,5,16,67,404,3904,64840,1930842,104698904, 10401039400,1900637187280,641429385018832, 401454435464761376,467919402404052870944, 1019758699013228238271040, 4171161230867751509749228304] |