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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 0 |
| 4 | 1 |
| 5 | 4 |
| 6 | 22 |
| 7 | 144 |
| 8 | 1089 |
| 9 | 9308 |
| 10 | 88562 |
| 11 | 927584 |
| 12 | 10603178 |
| 13 | 131368648 |
| 14 | 1753970380 |
| 15 | 25112732512 |
| 16 | 383925637137 |
| 17 | 6243618722124 |
| 18 | 107644162715098 |
| 19 | 1961478594977856 |
| 20 | 37671587406585006 |
| 21 | 760654555198989240 |
| 22 | 16110333600696417780 |
| 23 | 357148428086308848480 |
| 24 | 8271374327887650503130 |
[1,0,1,4,22,144,1089,9308,88562,927584,10603178, 131368648,1753970380,25112732512,383925637137, 6243618722124,107644162715098,1961478594977856, 37671587406585006,760654555198989240, 16110333600696417780,357148428086308848480, 8271374327887650503130] |