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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 39 |
| 6 | 104 |
| 7 | 281 |
| 8 | 771 |
| 9 | 2122 |
| 10 | 5858 |
| 11 | 16174 |
| 12 | 44694 |
| 13 | 123510 |
| 14 | 341403 |
| 15 | 943694 |
| 16 | 2608709 |
| 17 | 7211359 |
| 18 | 19935055 |
| 19 | 55108220 |
| 20 | 152341402 |
| 21 | 421132682 |
| 22 | 1164181573 |
| 23 | 3218268552 |
| 24 | 8896600238 |
| 25 | 24593808939 |
| 26 | 67987267220 |
| 27 | 187944382019 |
| 28 | 519554527901 |
[1,2,5,15,39,104,281,771,2122,5858,16174,44694, 123510,341403,943694,2608709,7211359,19935055, 55108220,152341402,421132682,1164181573, 3218268552,8896600238,24593808939,67987267220, 187944382019,519554527901] |