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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 77 |
| 6 | 285 |
| 7 | 1053 |
| 8 | 3875 |
| 9 | 14212 |
| 10 | 52021 |
| 11 | 190301 |
| 12 | 696532 |
| 13 | 2553047 |
| 14 | 9377034 |
| 15 | 34525630 |
| 16 | 127466481 |
| 17 | 471935813 |
| 18 | 1752332838 |
| 19 | 6525032251 |
| 20 | 24363932865 |
| 21 | 91214649344 |
| 22 | 342358204917 |
| 23 | 1288067835421 |
| 24 | 4857138874476 |
| 25 | 18354766803127 |
| 26 | 69500599635905 |
| 27 | 263661684179088 |
| 28 | 1002016365217651 |
[1,1,2,6,21,77,285,1053,3875,14212,52021,190301, 696532,2553047,9377034,34525630,127466481, 471935813,1752332838,6525032251,24363932865, 91214649344,342358204917,1288067835421, 4857138874476,18354766803127,69500599635905, 263661684179088,1002016365217651] |