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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 18 |
| 3 | 141 |
| 4 | 993 |
| 5 | 7330 |
| 6 | 54106 |
| 7 | 398654 |
| 8 | 2937795 |
| 9 | 21650600 |
| 10 | 159556133 |
| 11 | 1175862733 |
| 12 | 8665626722 |
| 13 | 63862119016 |
| 14 | 470637646700 |
| 15 | 3468406597875 |
| 16 | 25560735353400 |
| 17 | 188372145331363 |
| 18 | 1388225520347031 |
| 19 | 10230653220855076 |
| 20 | 75395721942360742 |
[1,18,141,993,7330,54106,398654,2937795,21650600, 159556133,1175862733,8665626722,63862119016, 470637646700,3468406597875,25560735353400, 188372145331363,1388225520347031, 10230653220855076,75395721942360742] |