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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 145 |
| 3 | 19016 |
| 4 | 6176676 |
| 5 | 4038562000 |
| 6 | 4664347807268 |
| 7 | 8698721212922496 |
| 8 | 24535712762777208384 |
| 9 | 99585504924929052560640 |
| 10 | 559305193643176161735904320 |
| 11 | 4211594966980674975033969246720 |
| 12 | 41428564066728305721531962537124096 |
| 13 | 520897493876353116313789796095643304960 |
[1,4,145,19016,6176676,4038562000,4664347807268, 8698721212922496,24535712762777208384, 99585504924929052560640, 559305193643176161735904320, 4211594966980674975033969246720, 41428564066728305721531962537124096, 520897493876353116313789796095643304960] |