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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 30 |
| 4 | 143 |
| 5 | 729 |
| 6 | 3891 |
| 7 | 21471 |
| 8 | 121505 |
| 9 | 701316 |
| 10 | 4112751 |
| 11 | 24435424 |
| 12 | 146773582 |
| 13 | 889813460 |
| 14 | 5437598036 |
| 15 | 33459382065 |
| 16 | 207138653334 |
| 17 | 1289231982454 |
| 18 | 8062548100445 |
| 19 | 50637167131635 |
| 20 | 319255808742145 |
| 21 | 2019867936975125 |
| 22 | 12819928874057325 |
| 23 | 81603361510347675 |
[1,2,7,30,143,729,3891,21471,121505,701316, 4112751,24435424,146773582,889813460,5437598036, 33459382065,207138653334,1289231982454, 8062548100445,50637167131635,319255808742145, 2019867936975125,12819928874057325, 81603361510347675] |