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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 12 |
| 3 | 60 |
| 4 | 420 |
| 5 | 4620 |
| 6 | 60060 |
| 7 | 1021020 |
| 8 | 19399380 |
| 9 | 446185740 |
| 10 | 12939386460 |
| 11 | 401120980260 |
| 12 | 14841476269620 |
| 13 | 608500527054420 |
| 14 | 26165522663340060 |
| 15 | 1229779565176982820 |
| 16 | 65178316954380089460 |
| 17 | 3845520700308425278140 |
| 18 | 234576762718813941966540 |
| 19 | 15716643102160534111758180 |
[1,4,12,60,420,4620,60060,1021020,19399380, 446185740,12939386460,401120980260,14841476269620, 608500527054420,26165522663340060, 1229779565176982820,65178316954380089460, 3845520700308425278140,234576762718813941966540, 15716643102160534111758180] |