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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 56 |
| 3 | 392 |
| 4 | 2744 |
| 5 | 19180 |
| 6 | 134064 |
| 7 | 937104 |
| 8 | 6550320 |
| 9 | 45786384 |
| 10 | 320044452 |
| 11 | 2237094216 |
| 12 | 15637173048 |
| 13 | 109303031880 |
| 14 | 764022547512 |
| 15 | 5340478146444 |
| 16 | 37329666414768 |
| 17 | 260932440209616 |
| 18 | 1823904280240560 |
| 19 | 12748996716570576 |
[1,8,56,392,2744,19180,134064,937104,6550320, 45786384,320044452,2237094216,15637173048, 109303031880,764022547512,5340478146444, 37329666414768,260932440209616,1823904280240560, 12748996716570576] |