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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 80 |
| 6 | 326 |
| 7 | 1566 |
| 8 | 9544 |
| 9 | 53696 |
| 10 | 347382 |
| 11 | 2566892 |
| 12 | 21907934 |
| 13 | 184868860 |
| 14 | 1704360992 |
| 15 | 17294597926 |
| 16 | 192725663600 |
| 17 | 2139133978996 |
[1,2,6,24,80,326,1566,9544,53696,347382,2566892, 21907934,184868860,1704360992,17294597926, 192725663600,2139133978996] |