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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 23 |
| 3 | 167 |
| 4 | 1370 |
| 5 | 12066 |
| 6 | 111399 |
| 7 | 1063896 |
| 8 | 10423145 |
| 9 | 104172842 |
| 10 | 1057938416 |
| 11 | 10886055709 |
| 12 | 113252336950 |
| 13 | 1189231665334 |
| 14 | 12588038915535 |
| 15 | 134172815937543 |
| 16 | 1438842536532522 |
| 17 | 15513036330871914 |
| 18 | 168057711839246901 |
| 19 | 1828443841807079994 |
| 20 | 19970180509170366264 |
| 21 | 218877585875869278396 |
[1,4,23,167,1370,12066,111399,1063896,10423145, 104172842,1057938416,10886055709,113252336950, 1189231665334,12588038915535,134172815937543, 1438842536532522,15513036330871914, 168057711839246901,1828443841807079994, 19970180509170366264,218877585875869278396] |