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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 21 |
| 4 | 80 |
| 5 | 275 |
| 6 | 1120 |
| 7 | 4164 |
| 8 | 17627 |
| 9 | 68636 |
| 10 | 297325 |
| 11 | 1194403 |
| 12 | 5261790 |
| 13 | 21631711 |
| 14 | 96502081 |
| 15 | 403736439 |
| 16 | 1818348174 |
| 17 | 7712720923 |
| 18 | 35000405956 |
| 19 | 150124914344 |
| 20 | 685486436315 |
| 21 | 2967502084569 |
| 22 | 13619251406030 |
| 23 | 59418422131252 |
| 24 | 273872899297569 |
| 25 | 1202825082289681 |
| 26 | 5564479952269571 |
| 27 | 24579592893740449 |
[1,2,7,21,80,275,1120,4164,17627,68636,297325, 1194403,5261790,21631711,96502081,403736439, 1818348174,7712720923,35000405956,150124914344, 685486436315,2967502084569,13619251406030, 59418422131252,273872899297569,1202825082289681, 5564479952269571,24579592893740449] |