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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 88 |
| 6 | 368 |
| 7 | 1584 |
| 8 | 6968 |
| 9 | 31192 |
| 10 | 141656 |
| 11 | 651136 |
| 12 | 3023840 |
| 13 | 14166496 |
| 14 | 66876096 |
| 15 | 317809216 |
| 16 | 1519163456 |
| 17 | 7299577216 |
| 18 | 35237444736 |
| 19 | 170812433536 |
| 20 | 831127053696 |
| 21 | 4057858988416 |
| 22 | 19873611712896 |
| 23 | 97609555091456 |
[1,1,2,6,22,88,368,1584,6968,31192,141656,651136, 3023840,14166496,66876096,317809216,1519163456, 7299577216,35237444736,170812433536,831127053696, 4057858988416,19873611712896,97609555091456] |