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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 71 |
| 6 | 209 |
| 7 | 545 |
| 8 | 1348 |
| 9 | 3270 |
| 10 | 7908 |
| 11 | 19201 |
| 12 | 46918 |
| 13 | 115407 |
| 14 | 285642 |
| 15 | 711031 |
| 16 | 1779289 |
| 17 | 4474537 |
| 18 | 11304830 |
| 19 | 28685778 |
| 20 | 73083753 |
| 21 | 186888321 |
| 22 | 479511547 |
| 23 | 1234006566 |
| 24 | 3184091383 |
| 25 | 8234890726 |
| 26 | 21340207949 |
| 27 | 55396690600 |
| 28 | 144013075958 |
[1,2,6,21,71,209,545,1348,3270,7908,19201,46918, 115407,285642,711031,1779289,4474537,11304830, 28685778,73083753,186888321,479511547,1234006566, 3184091383,8234890726,21340207949,55396690600, 144013075958] |