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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 19 |
| 7 | 60 |
| 8 | 194 |
| 9 | 628 |
| 10 | 2035 |
| 11 | 6597 |
| 12 | 21393 |
| 13 | 69382 |
| 14 | 225031 |
| 15 | 729865 |
| 16 | 2367255 |
| 17 | 7678002 |
| 18 | 24902998 |
| 19 | 80770936 |
| 20 | 261974262 |
| 21 | 849693202 |
| 22 | 2755914018 |
| 23 | 8938593456 |
| 24 | 28991634898 |
| 25 | 94032120191 |
| 26 | 304985891949 |
| 27 | 989198096368 |
[2,1,1,2,6,19,60,194,628,2035,6597,21393,69382, 225031,729865,2367255,7678002,24902998,80770936, 261974262,849693202,2755914018,8938593456, 28991634898,94032120191,304985891949,989198096368] |