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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 60 |
| 3 | 448 |
| 4 | 3360 |
| 5 | 25344 |
| 6 | 192192 |
| 7 | 1464320 |
| 8 | 11202048 |
| 9 | 85995520 |
| 10 | 662165504 |
| 11 | 5112102912 |
| 12 | 39557939200 |
| 13 | 306726174720 |
| 14 | 2382605107200 |
| 15 | 18537602088960 |
| 16 | 144438816276480 |
| 17 | 1126891074355200 |
| 18 | 8802271391907840 |
| 19 | 68829791335219200 |
| 20 | 538749548542033920 |
| 21 | 4220762508660572160 |
[1,8,60,448,3360,25344,192192,1464320,11202048, 85995520,662165504,5112102912,39557939200, 306726174720,2382605107200,18537602088960, 144438816276480,1126891074355200,8802271391907840, 68829791335219200,538749548542033920, 4220762508660572160] |