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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 22 |
| 3 | 70 |
| 4 | 211 |
| 5 | 637 |
| 6 | 1912 |
| 7 | 5740 |
| 8 | 17221 |
| 9 | 51667 |
| 10 | 155002 |
| 11 | 465010 |
| 12 | 1395031 |
| 13 | 4185097 |
| 14 | 12555292 |
| 15 | 37665880 |
| 16 | 112997641 |
| 17 | 338992927 |
| 18 | 1016978782 |
| 19 | 3050936350 |
| 20 | 9152809051 |
| 21 | 27458427157 |
| 22 | 82375281472 |
| 23 | 247125844420 |
| 24 | 741377533261 |
| 25 | 2224132599787 |
| 26 | 6672397799362 |
| 27 | 20017193398090 |
[1,7,22,70,211,637,1912,5740,17221,51667,155002, 465010,1395031,4185097,12555292,37665880, 112997641,338992927,1016978782,3050936350, 9152809051,27458427157,82375281472,247125844420, 741377533261,2224132599787,6672397799362, 20017193398090] |