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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 14 |
| 6 | 41 |
| 7 | 124 |
| 8 | 384 |
| 9 | 1211 |
| 10 | 3875 |
| 11 | 12548 |
| 12 | 41040 |
| 13 | 135370 |
| 14 | 449791 |
| 15 | 1504057 |
| 16 | 5057668 |
| 17 | 17092030 |
| 18 | 58018150 |
| 19 | 197727023 |
| 20 | 676290905 |
| 21 | 2320721255 |
| 22 | 7987481185 |
| 23 | 27566740439 |
| 24 | 95379299734 |
| 25 | 330774138321 |
| 26 | 1149589209136 |
| 27 | 4003322875481 |
[1,1,2,5,14,41,124,384,1211,3875,12548,41040, 135370,449791,1504057,5057668,17092030,58018150, 197727023,676290905,2320721255,7987481185, 27566740439,95379299734,330774138321, 1149589209136,4003322875481] |