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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 13 |
| 5 | 36 |
| 6 | 123 |
| 7 | 412 |
| 8 | 1504 |
| 9 | 5600 |
| 10 | 21399 |
| 11 | 84082 |
| 12 | 335325 |
| 13 | 1365925 |
| 14 | 5631945 |
| 15 | 23526240 |
| 16 | 99401707 |
| 17 | 423998705 |
| 18 | 1825605301 |
| 19 | 7920044895 |
| 20 | 34608734002 |
| 21 | 152221362735 |
| 22 | 673469046190 |
| 23 | 2996014337863 |
| 24 | 13393435660905 |
| 25 | 60149049644269 |
| 26 | 271270358104602 |
| 27 | 1228214195018762 |
| 28 | 5581224940035092 |
[1,1,2,4,13,36,123,412,1504,5600,21399,84082, 335325,1365925,5631945,23526240,99401707, 423998705,1825605301,7920044895,34608734002, 152221362735,673469046190,2996014337863, 13393435660905,60149049644269,271270358104602, 1228214195018762,5581224940035092] |