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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 33 |
| 5 | 100 |
| 6 | 305 |
| 7 | 937 |
| 8 | 2890 |
| 9 | 8943 |
| 10 | 27741 |
| 11 | 86216 |
| 12 | 268355 |
| 13 | 836297 |
| 14 | 2608818 |
| 15 | 8144875 |
| 16 | 25446229 |
| 17 | 79545148 |
| 18 | 248780979 |
| 19 | 778400001 |
| 20 | 2436380402 |
| 21 | 7628211951 |
| 22 | 23890103153 |
| 23 | 74836927720 |
| 24 | 234478937321 |
| 25 | 734802907841 |
| 26 | 2303073316042 |
[1,1,4,11,33,100,305,937,2890,8943,27741,86216, 268355,836297,2608818,8144875,25446229,79545148, 248780979,778400001,2436380402,7628211951, 23890103153,74836927720,234478937321,734802907841, 2303073316042] |