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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 132 |
| 3 | 3080 |
| 4 | 57360 |
| 5 | 983072 |
| 6 | 16252992 |
| 7 | 264241280 |
| 8 | 4261413120 |
| 9 | 68451041792 |
| 10 | 1097364145152 |
| 11 | 17575006177280 |
| 12 | 281337537761280 |
| 13 | 4502500115750912 |
| 14 | 72048797944922112 |
| 15 | 1152851135862702080 |
| 16 | 18446181123756195840 |
| 17 | 295143401579725586432 |
| 18 | 4722330454072626511872 |
[0,2,132,3080,57360,983072,16252992,264241280, 4261413120,68451041792,1097364145152, 17575006177280,281337537761280,4502500115750912, 72048797944922112,1152851135862702080, 18446181123756195840,295143401579725586432, 4722330454072626511872] |