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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 216 |
| 3 | 7371 |
| 4 | 239424 |
| 5 | 8127875 |
| 6 | 296315496 |
| 7 | 11685617608 |
| 8 | 498593804800 |
| 9 | 22959117809685 |
| 10 | 1137033860419000 |
| 11 | 60338078785131785 |
| 12 | 3418430599382500800 |
| 13 | 206053517402599981504 |
| 14 | 13172124530670958537160 |
| 15 | 890361160360138336174875 |
| 16 | 63463906792476058870550528 |
| 17 | 4758276450884470061869230823 |
[0,4,216,7371,239424,8127875,296315496, 11685617608,498593804800,22959117809685, 1137033860419000,60338078785131785, 3418430599382500800,206053517402599981504, 13172124530670958537160,890361160360138336174875, 63463906792476058870550528, 4758276450884470061869230823] |