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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 56 |
| 3 | 392 |
| 4 | 2696 |
| 5 | 18584 |
| 6 | 127160 |
| 7 | 871256 |
| 8 | 5946200 |
| 9 | 40613816 |
| 10 | 276750536 |
| 11 | 1886784200 |
| 12 | 12843449288 |
| 13 | 87456597656 |
| 14 | 594876193016 |
| 15 | 4047352264616 |
| 16 | 27514497698984 |
| 17 | 187083712725224 |
| 18 | 1271271096363128 |
| 19 | 8639846411760440 |
| 20 | 58689235680164600 |
| 21 | 398715967140863864 |
[1,8,56,392,2696,18584,127160,871256,5946200, 40613816,276750536,1886784200,12843449288, 87456597656,594876193016,4047352264616, 27514497698984,187083712725224,1271271096363128, 8639846411760440,58689235680164600, 398715967140863864] |