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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 26 |
| 3 | 612 |
| 4 | 26919 |
| 5 | 1603680 |
| 6 | 117660064 |
| 7 | 10162944112 |
| 8 | 1005838347950 |
| 9 | 112009295740916 |
| 10 | 13850874442895434 |
| 11 | 1882848486231714788 |
| 12 | 279100448753985866813 |
| 13 | 44813411860476850508720 |
| 14 | 7749809454081027489860264 |
| 15 | 1436399220794697421878462832 |
| 16 | 284111046278259235057207651469 |
| 17 | 59740768193467931633275499487660 |
| 18 | 13308884562229489858971683010469182 |
| 19 | 3131623636896229572958776700673759164 |
[1,4,26,612,26919,1603680,117660064,10162944112, 1005838347950,112009295740916,13850874442895434, 1882848486231714788,279100448753985866813, 44813411860476850508720,7749809454081027489860264, 1436399220794697421878462832, 284111046278259235057207651469, 59740768193467931633275499487660, 13308884562229489858971683010469182, 3131623636896229572958776700673759164] |