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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 22 |
| 5 | 80 |
| 6 | 265 |
| 7 | 888 |
| 8 | 3336 |
| 9 | 12249 |
| 10 | 45072 |
| 11 | 173673 |
| 12 | 672941 |
| 13 | 2595981 |
| 14 | 10244208 |
| 15 | 41012730 |
| 16 | 162936518 |
| 17 | 655570981 |
| 18 | 2678127981 |
| 19 | 10874155875 |
| 20 | 44444744731 |
| 21 | 183974555899 |
| 22 | 759720059015 |
| 23 | 3144923360494 |
| 24 | 13144320477323 |
| 25 | 54991936410992 |
| 26 | 230045973211635 |
| 27 | 969001518828255 |
| 28 | 4094574894059769 |
[1,1,3,8,22,80,265,888,3336,12249,45072,173673, 672941,2595981,10244208,41012730,162936518, 655570981,2678127981,10874155875,44444744731, 183974555899,759720059015,3144923360494, 13144320477323,54991936410992,230045973211635, 969001518828255,4094574894059769] |