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| n | a(n) |
|---|---|
| 1 | 18 |
| 2 | 56 |
| 3 | 150 |
| 4 | 446 |
| 5 | 1232 |
| 6 | 3602 |
| 7 | 10108 |
| 8 | 29272 |
| 9 | 82854 |
| 10 | 238640 |
| 11 | 678658 |
| 12 | 1948718 |
| 13 | 5556204 |
| 14 | 15926754 |
| 15 | 45474920 |
| 16 | 130227048 |
| 17 | 372121034 |
| 18 | 1065071288 |
| 19 | 3044724350 |
| 20 | 8711869630 |
| 21 | 24910552504 |
| 22 | 71264572098 |
| 23 | 203799138404 |
| 24 | 582977750488 |
| 25 | 1667293062110 |
[18,56,150,446,1232,3602,10108,29272,82854,238640, 678658,1948718,5556204,15926754,45474920, 130227048,372121034,1065071288,3044724350, 8711869630,24910552504,71264572098,203799138404, 582977750488,1667293062110] |