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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 32 |
| 5 | 168 |
| 6 | 1184 |
| 7 | 8622 |
| 8 | 77216 |
| 9 | 747576 |
| 10 | 8185392 |
| 11 | 93054960 |
| 12 | 1264465872 |
| 13 | 16974221184 |
| 14 | 254355732864 |
| 15 | 4069961945280 |
| 16 | 70258008510720 |
| 17 | 1228263760984320 |
| 18 | 24025502406873600 |
| 19 | 470522155226595840 |
| 20 | 10095034628228958720 |
| 21 | 222277023267825254400 |
| 22 | 5144511652272759029760 |
[1,1,2,7,32,168,1184,8622,77216,747576,8185392, 93054960,1264465872,16974221184,254355732864, 4069961945280,70258008510720,1228263760984320, 24025502406873600,470522155226595840, 10095034628228958720,222277023267825254400, 5144511652272759029760] |