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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 32 |
| 6 | 189 |
| 7 | 1382 |
| 8 | 12090 |
| 9 | 123220 |
| 10 | 1433760 |
| 11 | 18750856 |
| 12 | 272243150 |
| 13 | 4344694984 |
| 14 | 75590125814 |
| 15 | 1423923579636 |
| 16 | 28872306351182 |
| 17 | 626986388773656 |
| 18 | 14518030696953650 |
| 19 | 357068944503961140 |
| 20 | 9296168815245928682 |
| 21 | 255409012110904594768 |
| 22 | 7385107814017356745382 |
[1,0,1,2,7,32,189,1382,12090,123220,1433760, 18750856,272243150,4344694984,75590125814, 1423923579636,28872306351182,626986388773656, 14518030696953650,357068944503961140, 9296168815245928682,255409012110904594768, 7385107814017356745382] |