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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 9 |
| 6 | 20 |
| 7 | 73 |
| 8 | 328 |
| 9 | 1655 |
| 10 | 10746 |
| 11 | 103583 |
| 12 | 974458 |
| 13 | 13360226 |
| 14 | 192146495 |
| 15 | 4002035013 |
| 16 | 89158887545 |
| 17 | 2840078369454 |
[1,1,1,1,9,20,73,328,1655,10746,103583,974458, 13360226,192146495,4002035013,89158887545, 2840078369454] |