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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 15 |
| 3 | 92 |
| 4 | 615 |
| 5 | 4200 |
| 6 | 29190 |
| 7 | 205416 |
| 8 | 1458909 |
| 9 | 10436030 |
| 10 | 75079719 |
| 11 | 542669244 |
| 12 | 3937604853 |
| 13 | 28664996080 |
| 14 | 209261546580 |
| 15 | 1531373181120 |
| 16 | 11230365782130 |
| 17 | 82512324300222 |
| 18 | 607246350958449 |
| 19 | 4475646134515360 |
| 20 | 33031356134381220 |
| 21 | 244073892799489500 |
| 22 | 1805479496422561740 |
[1,2,15,92,615,4200,29190,205416,1458909,10436030, 75079719,542669244,3937604853,28664996080, 209261546580,1531373181120,11230365782130, 82512324300222,607246350958449,4475646134515360, 33031356134381220,244073892799489500, 1805479496422561740] |