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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 27 |
| 5 | 270 |
| 6 | 3645 |
| 7 | 62370 |
| 8 | 1295595 |
| 9 | 31689630 |
| 10 | 892387125 |
| 11 | 28439784450 |
| 12 | 1011998000475 |
| 13 | 39773696712750 |
| 14 | 1711186282730925 |
| 15 | 79990996596761250 |
| 16 | 4037168079574504875 |
| 17 | 218797477268743122750 |
| 18 | 12673229445076108033125 |
[0,1,4,27,270,3645,62370,1295595,31689630, 892387125,28439784450,1011998000475, 39773696712750,1711186282730925,79990996596761250, 4037168079574504875,218797477268743122750, 12673229445076108033125] |