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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 4 |
| 6 | 12 |
| 7 | 27 |
| 8 | 82 |
| 9 | 224 |
| 10 | 708 |
| 11 | 2158 |
| 12 | 6950 |
| 13 | 22315 |
| 14 | 73221 |
| 15 | 241386 |
| 16 | 804944 |
| 17 | 2699671 |
| 18 | 9121604 |
| 19 | 30986147 |
| 20 | 105843040 |
| 21 | 363233296 |
| 22 | 1252126688 |
[1,1,1,3,4,12,27,82,224,708,2158,6950,22315,73221, 241386,804944,2699671,9121604,30986147,105843040, 363233296,1252126688] |