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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 7 |
| 6 | 25 |
| 7 | 79 |
| 8 | 339 |
| 9 | 1351 |
| 10 | 6721 |
| 11 | 31831 |
| 12 | 179643 |
| 13 | 979567 |
| 14 | 6166105 |
| 15 | 37852039 |
| 16 | 262308819 |
| 17 | 1784037031 |
| 18 | 13471274401 |
| 19 | 100285059751 |
| 20 | 818288740923 |
| 21 | 6604485845167 |
| 22 | 57836113793305 |
| 23 | 502235849694679 |
| 24 | 4693153430067699 |
| 25 | 43572170967012871 |
| 26 | 432360767273547841 |
[1,0,1,1,3,7,25,79,339,1351,6721,31831,179643, 979567,6166105,37852039,262308819,1784037031, 13471274401,100285059751,818288740923, 6604485845167,57836113793305,502235849694679, 4693153430067699,43572170967012871, 432360767273547841] |