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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 3 |
| 3 | 20 |
| 4 | 188 |
| 5 | 2280 |
| 6 | 33864 |
| 7 | 595196 |
| 8 | 12081600 |
| 9 | 278122032 |
| 10 | 7159299200 |
| 11 | 203771364324 |
| 12 | 6354217539072 |
| 13 | 215429796291320 |
| 14 | 7889813961243648 |
| 15 | 310413633428119500 |
| 16 | 13057068314325008384 |
| 17 | 584737112800511959104 |
| 18 | 27776659696045110558720 |
| 19 | 1395009275793285886030772 |
| 20 | 73854320834079368232960000 |
[0,0,3,20,188,2280,33864,595196,12081600, 278122032,7159299200,203771364324,6354217539072, 215429796291320,7889813961243648, 310413633428119500,13057068314325008384, 584737112800511959104,27776659696045110558720, 1395009275793285886030772, 73854320834079368232960000] |