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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 16 |
| 3 | 170 |
| 4 | 1920 |
| 5 | 22402 |
| 6 | 266800 |
| 7 | 3222634 |
| 8 | 39328768 |
| 9 | 483752258 |
| 10 | 5987236816 |
| 11 | 74474238698 |
| 12 | 930212870784 |
| 13 | 11659157743170 |
| 14 | 146567181170160 |
| 15 | 1847198697449770 |
| 16 | 23332153206562816 |
| 17 | 295286370825453442 |
| 18 | 3743540075432798608 |
| 19 | 47532529217041519658 |
| 20 | 604366048841146280320 |
[1,2,16,170,1920,22402,266800,3222634,39328768, 483752258,5987236816,74474238698,930212870784, 11659157743170,146567181170160,1847198697449770, 23332153206562816,295286370825453442, 3743540075432798608,47532529217041519658, 604366048841146280320] |