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| n | a(n) |
|---|---|
| 1 | 18 |
| 2 | 189 |
| 3 | 1296 |
| 4 | 7290 |
| 5 | 36450 |
| 6 | 168399 |
| 7 | 734832 |
| 8 | 3070548 |
| 9 | 12400290 |
| 10 | 48715425 |
| 11 | 187067232 |
| 12 | 704690766 |
| 13 | 2611501074 |
| 14 | 9542023155 |
| 15 | 34437376800 |
| 16 | 122941435176 |
| 17 | 434685788658 |
| 18 | 1523724783237 |
| 19 | 5299912289520 |
| 20 | 18305618105250 |
| 21 | 62824881337218 |
| 22 | 214364018189079 |
| 23 | 727538485975056 |
[18,189,1296,7290,36450,168399,734832,3070548, 12400290,48715425,187067232,704690766,2611501074, 9542023155,34437376800,122941435176,434685788658, 1523724783237,5299912289520,18305618105250, 62824881337218,214364018189079,727538485975056] |