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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 216 |
| 3 | 2136 |
| 4 | 18864 |
| 5 | 154656 |
| 6 | 1203072 |
| 7 | 9000576 |
| 8 | 65339136 |
| 9 | 463112704 |
| 10 | 3219204096 |
| 11 | 22019254272 |
| 12 | 148577427456 |
| 13 | 990973034496 |
| 14 | 6543595044864 |
| 15 | 42832379117568 |
| 16 | 278217855664128 |
| 17 | 1794871415144448 |
| 18 | 11508930723708928 |
[1,18,216,2136,18864,154656,1203072,9000576, 65339136,463112704,3219204096,22019254272, 148577427456,990973034496,6543595044864, 42832379117568,278217855664128,1794871415144448, 11508930723708928] |