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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 48 |
| 4 | 336 |
| 5 | 2560 |
| 6 | 20608 |
| 7 | 172432 |
| 8 | 1484704 |
| 9 | 13069296 |
| 10 | 117080576 |
| 11 | 1063944416 |
| 12 | 9783594304 |
| 13 | 90869069872 |
| 14 | 851218195008 |
| 15 | 8032861976544 |
| 16 | 76295247548480 |
| 17 | 728766670652368 |
| 18 | 6996258626856320 |
| 19 | 67467783946608064 |
| 20 | 653254749175955584 |
| 21 | 6348266152788407648 |
| 22 | 61896814517299122560 |
[1,2,8,48,336,2560,20608,172432,1484704,13069296, 117080576,1063944416,9783594304,90869069872, 851218195008,8032861976544,76295247548480, 728766670652368,6996258626856320, 67467783946608064,653254749175955584, 6348266152788407648,61896814517299122560] |