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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 23 |
| 4 | 68 |
| 5 | 200 |
| 6 | 615 |
| 7 | 1764 |
| 8 | 5060 |
| 9 | 14626 |
| 10 | 41785 |
| 11 | 117573 |
| 12 | 332475 |
| 13 | 933891 |
| 14 | 2609832 |
| 15 | 7278512 |
[1,2,7,23,68,200,615,1764,5060,14626,41785,117573, 332475,933891,2609832,7278512] |