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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 25 |
| 5 | 69 |
| 6 | 189 |
| 7 | 519 |
| 8 | 1428 |
| 9 | 3930 |
| 10 | 10812 |
| 11 | 29742 |
| 12 | 81816 |
| 13 | 225070 |
| 14 | 619156 |
| 15 | 1703262 |
| 16 | 4685565 |
| 17 | 12889687 |
| 18 | 35458707 |
| 19 | 97544655 |
| 20 | 268339161 |
| 21 | 738183999 |
| 22 | 2030697309 |
| 23 | 5586319365 |
| 24 | 15367609920 |
| 25 | 42275319276 |
| 26 | 116296719448 |
[1,1,3,9,25,69,189,519,1428,3930,10812,29742, 81816,225070,619156,1703262,4685565,12889687, 35458707,97544655,268339161,738183999,2030697309, 5586319365,15367609920,42275319276,116296719448] |