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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 57 |
| 5 | 164 |
| 6 | 485 |
| 7 | 1424 |
| 8 | 4169 |
| 9 | 12228 |
| 10 | 35868 |
| 11 | 105177 |
| 12 | 308433 |
| 13 | 904520 |
| 14 | 2652574 |
| 15 | 7778858 |
| 16 | 22812126 |
| 17 | 66898367 |
| 18 | 196184665 |
| 19 | 575326896 |
| 20 | 1687191264 |
| 21 | 4947820577 |
| 22 | 14509871545 |
| 23 | 42551335553 |
| 24 | 124785126404 |
| 25 | 365942162811 |
| 26 | 1073154072467 |
[2,6,20,57,164,485,1424,4169,12228,35868,105177, 308433,904520,2652574,7778858,22812126,66898367, 196184665,575326896,1687191264,4947820577, 14509871545,42551335553,124785126404,365942162811, 1073154072467] |