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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 61 |
| 5 | 210 |
| 6 | 775 |
| 7 | 2880 |
| 8 | 11167 |
| 9 | 43450 |
| 10 | 174162 |
| 11 | 699434 |
| 12 | 2871416 |
| 13 | 11799186 |
| 14 | 49318291 |
| 15 | 206225105 |
| 16 | 874196472 |
| 17 | 3706064495 |
| 18 | 15889015969 |
| 19 | 68112992527 |
| 20 | 294754698073 |
| 21 | 1275221193581 |
| 22 | 5561717925056 |
| 23 | 24248871644687 |
| 24 | 106464002206487 |
| 25 | 467252246935953 |
| 26 | 2063253080723396 |
| 27 | 9107050843279229 |
[1,2,6,18,61,210,775,2880,11167,43450,174162, 699434,2871416,11799186,49318291,206225105, 874196472,3706064495,15889015969,68112992527, 294754698073,1275221193581,5561717925056, 24248871644687,106464002206487,467252246935953, 2063253080723396,9107050843279229] |