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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 18 |
| 3 | 19 |
| 4 | 56 |
| 5 | 203 |
| 6 | 672 |
| 7 | 2168 |
| 8 | 7287 |
| 9 | 25652 |
| 10 | 88027 |
| 11 | 306375 |
| 12 | 1070802 |
| 13 | 3744286 |
| 14 | 13105674 |
| 15 | 45926952 |
| 16 | 161012379 |
| 17 | 564504898 |
| 18 | 1979855821 |
| 19 | 6944885024 |
| 20 | 24362969123 |
| 21 | 85473134558 |
| 22 | 299883787584 |
| 23 | 1052181830655 |
| 24 | 3691806167058 |
| 25 | 12953760142043 |
[1,18,19,56,203,672,2168,7287,25652,88027,306375, 1070802,3744286,13105674,45926952,161012379, 564504898,1979855821,6944885024,24362969123, 85473134558,299883787584,1052181830655, 3691806167058,12953760142043] |