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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 5 |
| 6 | 14 |
| 7 | 44 |
| 8 | 139 |
| 9 | 475 |
| 10 | 1658 |
| 11 | 6146 |
| 12 | 23495 |
| 13 | 93840 |
| 14 | 385956 |
| 15 | 1643862 |
| 16 | 7193783 |
| 17 | 32446635 |
| 18 | 150049734 |
| 19 | 712619582 |
| 20 | 3462870079 |
[0,0,1,2,5,14,44,139,475,1658,6146,23495,93840, 385956,1643862,7193783,32446635,150049734, 712619582,3462870079] |