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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 75 |
| 6 | 255 |
| 7 | 813 |
| 8 | 2443 |
| 9 | 6985 |
| 10 | 19175 |
| 11 | 50917 |
| 12 | 131555 |
| 13 | 332257 |
| 14 | 823263 |
| 15 | 2007005 |
| 16 | 4825051 |
| 17 | 11460569 |
| 18 | 26935255 |
| 19 | 62717909 |
| 20 | 144834515 |
| 21 | 332005329 |
| 22 | 756023247 |
| 23 | 1711275981 |
| 24 | 3852468171 |
| 25 | 8629780425 |
| 26 | 19243466695 |
| 27 | 42731569093 |
| 28 | 94522834883 |
[1,2,6,21,75,255,813,2443,6985,19175,50917,131555, 332257,823263,2007005,4825051,11460569,26935255, 62717909,144834515,332005329,756023247,1711275981, 3852468171,8629780425,19243466695,42731569093, 94522834883] |