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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 16 |
| 4 | 80 |
| 5 | 512 |
| 6 | 3904 |
| 7 | 34816 |
| 8 | 354560 |
| 9 | 4063232 |
| 10 | 51733504 |
| 11 | 724566016 |
| 12 | 11070525440 |
| 13 | 183240753152 |
| 14 | 3266330312704 |
| 15 | 62382319599616 |
| 16 | 1270842139934720 |
| 17 | 27507470234550272 |
| 18 | 630424777638805504 |
| 19 | 15250953398036463616 |
| 20 | 388362339077351014400 |
| 21 | 10384044045105304174592 |
[1,2,4,16,80,512,3904,34816,354560,4063232, 51733504,724566016,11070525440,183240753152, 3266330312704,62382319599616,1270842139934720, 27507470234550272,630424777638805504, 15250953398036463616,388362339077351014400, 10384044045105304174592] |