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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 20 |
| 2 | 252 |
| 3 | 3432 |
| 4 | 48620 |
| 5 | 705432 |
| 6 | 10400600 |
| 7 | 155117520 |
| 8 | 2333606220 |
| 9 | 35345263800 |
| 10 | 538257874440 |
| 11 | 8233430727600 |
| 12 | 126410606437752 |
| 13 | 1946939425648112 |
| 14 | 30067266499541040 |
| 15 | 465428353255261088 |
| 16 | 7219428434016265740 |
| 17 | 112186277816662845432 |
| 18 | 1746130564335626209832 |
| 19 | 27217014869199032015600 |
[2,20,252,3432,48620,705432,10400600,155117520, 2333606220,35345263800,538257874440,8233430727600, 126410606437752,1946939425648112, 30067266499541040,465428353255261088, 7219428434016265740,112186277816662845432, 1746130564335626209832,27217014869199032015600] |