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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 31 |
| 3 | 1209 |
| 4 | 87510 |
| 5 | 10062642 |
| 6 | 1676297196 |
| 7 | 380613039300 |
| 8 | 112785012934704 |
| 9 | 42220061283665808 |
| 10 | 19466179705605460320 |
| 11 | 10832183496342326864160 |
| 12 | 7154687325911822697398400 |
| 13 | 5531732531984974533825018240 |
| 14 | 4947671342477051367102277159680 |
| 15 | 5067624845854754327998998304876800 |
[0,2,31,1209,87510,10062642,1676297196, 380613039300,112785012934704,42220061283665808, 19466179705605460320,10832183496342326864160, 7154687325911822697398400, 5531732531984974533825018240, 4947671342477051367102277159680, 5067624845854754327998998304876800] |