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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 9 |
| 6 | 20 |
| 7 | 49 |
| 8 | 119 |
| 9 | 305 |
| 10 | 790 |
| 11 | 2100 |
| 12 | 5648 |
| 13 | 15449 |
| 14 | 42664 |
| 15 | 119128 |
| 16 | 335310 |
| 17 | 951119 |
| 18 | 2714974 |
| 19 | 7795211 |
| 20 | 22493655 |
| 21 | 65202995 |
| 22 | 189767806 |
| 23 | 554326057 |
| 24 | 1624572250 |
| 25 | 4775504516 |
| 26 | 14076385819 |
| 27 | 41596613660 |
| 28 | 123206155126 |
[1,1,2,4,9,20,49,119,305,790,2100,5648,15449, 42664,119128,335310,951119,2714974,7795211, 22493655,65202995,189767806,554326057,1624572250, 4775504516,14076385819,41596613660,123206155126] |