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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 40 |
| 4 | 355 |
| 5 | 4425 |
| 6 | 69521 |
| 7 | 1162951 |
| 8 | 22259414 |
| 9 | 478096938 |
| 10 | 11614132907 |
| 11 | 299700810545 |
| 12 | 8456607358157 |
| 13 | 255883964141333 |
| 14 | 8275199908539114 |
| 15 | 287869753459458468 |
| 16 | 10564476589147507523 |
| 17 | 409845503129745719513 |
| 18 | 16777378294629533764699 |
| 19 | 720626728499888159724831 |
[1,1,4,40,355,4425,69521,1162951,22259414, 478096938,11614132907,299700810545,8456607358157, 255883964141333,8275199908539114, 287869753459458468,10564476589147507523, 409845503129745719513,16777378294629533764699, 720626728499888159724831] |