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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 26 |
| 6 | 126 |
| 7 | 640 |
| 8 | 3559 |
| 9 | 20366 |
| 10 | 120535 |
| 11 | 727292 |
| 12 | 4468614 |
| 13 | 27842644 |
| 14 | 175644673 |
| 15 | 1119847820 |
| 16 | 7207062667 |
| 17 | 46769169830 |
| 18 | 305762838483 |
| 19 | 2012363156332 |
| 20 | 13324398048658 |
| 21 | 88709165046956 |
| 22 | 593555082569368 |
| 23 | 3989727169508528 |
[1,1,2,7,26,126,640,3559,20366,120535,727292, 4468614,27842644,175644673,1119847820,7207062667, 46769169830,305762838483,2012363156332, 13324398048658,88709165046956,593555082569368, 3989727169508528] |