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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 3 |
| 3 | 8 |
| 4 | 26 |
| 5 | 138 |
| 6 | 611 |
| 7 | 2880 |
| 8 | 13727 |
| 9 | 65070 |
| 10 | 310816 |
| 11 | 1482870 |
| 12 | 7081007 |
| 13 | 33819984 |
| 14 | 161533363 |
| 15 | 771590878 |
| 16 | 3685656306 |
| 17 | 17605479026 |
| 18 | 84097488439 |
| 19 | 401715732434 |
| 20 | 1918912755293 |
| 21 | 9166251659440 |
| 22 | 43785309700922 |
| 23 | 209153493108094 |
[0,3,8,26,138,611,2880,13727,65070,310816,1482870, 7081007,33819984,161533363,771590878,3685656306, 17605479026,84097488439,401715732434, 1918912755293,9166251659440,43785309700922, 209153493108094] |