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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 36 |
| 6 | 216 |
| 7 | 1296 |
| 8 | 10368 |
| 9 | 78912 |
| 10 | 634896 |
| 11 | 5572656 |
| 12 | 51817536 |
| 13 | 477672768 |
| 14 | 8268884352 |
| 15 | 101752505856 |
| 16 | 1417554660096 |
| 17 | 20985416983296 |
| 18 | 344834432195328 |
| 19 | 5096129755468032 |
| 20 | 70148917686998016 |
[1,1,1,3,12,36,216,1296,10368,78912,634896, 5572656,51817536,477672768,8268884352, 101752505856,1417554660096,20985416983296, 344834432195328,5096129755468032, 70148917686998016] |