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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 73 |
| 5 | 271 |
| 6 | 1064 |
| 7 | 4212 |
| 8 | 17196 |
| 9 | 70596 |
| 10 | 296012 |
| 11 | 1245082 |
| 12 | 5318268 |
| 13 | 22764797 |
| 14 | 98594587 |
| 15 | 427635358 |
| 16 | 1872119304 |
| 17 | 8204325414 |
| 18 | 36227766180 |
| 19 | 160091182728 |
| 20 | 711920762932 |
| 21 | 3167656255528 |
| 22 | 14169825390905 |
| 23 | 63412119597744 |
| 24 | 285085092838761 |
| 25 | 1282074973042071 |
| 26 | 5788791384218925 |
| 27 | 26143617239786913 |
[1,2,6,20,73,271,1064,4212,17196,70596,296012, 1245082,5318268,22764797,98594587,427635358, 1872119304,8204325414,36227766180,160091182728, 711920762932,3167656255528,14169825390905, 63412119597744,285085092838761,1282074973042071, 5788791384218925,26143617239786913] |