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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 306 |
| 3 | 5202 |
| 4 | 88434 |
| 5 | 1503378 |
| 6 | 25557426 |
| 7 | 434476242 |
| 8 | 7386096114 |
| 9 | 125563633938 |
| 10 | 2134581776946 |
| 11 | 36287890208082 |
| 12 | 616894133537394 |
| 13 | 10487200270135698 |
| 14 | 178282404592306866 |
| 15 | 3030800878069216722 |
| 16 | 51523614927176684274 |
| 17 | 875901453762003632658 |
| 18 | 14890324713954061755186 |
[1,18,306,5202,88434,1503378,25557426,434476242, 7386096114,125563633938,2134581776946, 36287890208082,616894133537394,10487200270135698, 178282404592306866,3030800878069216722, 51523614927176684274,875901453762003632658, 14890324713954061755186] |