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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 306 |
| 3 | 5185 |
| 4 | 87840 |
| 5 | 1488096 |
| 6 | 25209793 |
| 7 | 427078386 |
| 8 | 7235122770 |
| 9 | 122570008705 |
| 10 | 2076455025216 |
| 11 | 35177165419968 |
| 12 | 595935357114241 |
| 13 | 10095723905522130 |
| 14 | 171031371036761970 |
| 15 | 2897437583719431361 |
| 16 | 49085407552193571168 |
[1,18,306,5185,87840,1488096,25209793,427078386, 7235122770,122570008705,2076455025216, 35177165419968,595935357114241,10095723905522130, 171031371036761970,2897437583719431361, 49085407552193571168] |