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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 23 |
| 4 | 75 |
| 5 | 241 |
| 6 | 777 |
| 7 | 2512 |
| 8 | 8132 |
| 9 | 26335 |
| 10 | 85263 |
| 11 | 276002 |
| 12 | 893434 |
| 13 | 2892149 |
| 14 | 9362316 |
| 15 | 30307241 |
| 16 | 98109034 |
| 17 | 317593232 |
| 18 | 1028095430 |
| 19 | 3328094579 |
| 20 | 10773527296 |
| 21 | 34875478670 |
| 22 | 112897008686 |
| 23 | 365464073909 |
| 24 | 1183060479295 |
| 25 | 3829739222562 |
[2,6,23,75,241,777,2512,8132,26335,85263,276002, 893434,2892149,9362316,30307241,98109034, 317593232,1028095430,3328094579,10773527296, 34875478670,112897008686,365464073909, 1183060479295,3829739222562] |