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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 9 |
| 7 | 21 |
| 8 | 73 |
| 9 | 310 |
| 10 | 1107 |
| 11 | 5232 |
| 12 | 33319 |
| 13 | 240772 |
| 14 | 2106289 |
| 15 | 21011261 |
| 16 | 262231181 |
| 17 | 3633528079 |
| 18 | 62517538899 |
[1,1,1,1,1,9,21,73,310,1107,5232,33319,240772, 2106289,21011261,262231181,3633528079,62517538899] |