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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 12 |
| 5 | 24 |
| 6 | 54 |
| 7 | 108 |
| 8 | 246 |
| 9 | 510 |
| 10 | 1218 |
| 11 | 2742 |
| 12 | 6930 |
| 13 | 16242 |
| 14 | 47706 |
| 15 | 144018 |
| 16 | 672732 |
| 17 | 2756124 |
| 18 | 5656266 |
| 19 | 27943404 |
| 20 | 75554226 |
| 21 | 661653378 |
| 22 | 1323306756 |
[1,2,6,12,24,54,108,246,510,1218,2742,6930,16242, 47706,144018,672732,2756124,5656266,27943404, 75554226,661653378,1323306756] |