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| n | a(n) |
|---|---|
| 2 | 4 |
| 3 | 84 |
| 4 | 1428 |
| 5 | 23188 |
| 6 | 372372 |
| 7 | 5963412 |
| 8 | 95436436 |
| 9 | 1527070356 |
| 10 | 24433475220 |
| 11 | 390937001620 |
| 12 | 6254997618324 |
| 13 | 100079984262804 |
| 14 | 1601279837683348 |
| 15 | 25620477760847508 |
| 16 | 409927645605215892 |
| 17 | 6558842335410077332 |
| 18 | 104941477389467729556 |
[4,84,1428,23188,372372,5963412,95436436, 1527070356,24433475220,390937001620,6254997618324, 100079984262804,1601279837683348, 25620477760847508,409927645605215892, 6558842335410077332,104941477389467729556] |