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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 22 |
| 5 | 59 |
| 6 | 170 |
| 7 | 525 |
| 8 | 1716 |
| 9 | 5917 |
| 10 | 21362 |
| 11 | 80533 |
| 12 | 315516 |
| 13 | 1281913 |
| 14 | 5383622 |
| 15 | 23330405 |
| 16 | 104084736 |
| 17 | 477371217 |
| 18 | 2246811730 |
| 19 | 10839493637 |
| 20 | 53528916508 |
| 21 | 270318789249 |
| 22 | 1394426035918 |
| 23 | 7341439399397 |
| 24 | 39413238225512 |
| 25 | 215607783811041 |
[1,2,4,9,22,59,170,525,1716,5917,21362,80533, 315516,1281913,5383622,23330405,104084736, 477371217,2246811730,10839493637,53528916508, 270318789249,1394426035918,7341439399397, 39413238225512,215607783811041] |