| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 20 |
| 3 | 208 |
| 4 | 2376 |
| 5 | 27346 |
| 6 | 313944 |
| 7 | 3607664 |
| 8 | 41448458 |
| 9 | 476228082 |
| 10 | 5471653976 |
| 11 | 62867030958 |
| 12 | 722316016670 |
| 13 | 8299110691962 |
| 14 | 95353331221526 |
| 15 | 1095570130851502 |
| 16 | 12587645301298246 |
| 17 | 144626810987686256 |
| 18 | 1661701927233901422 |
[0,20,208,2376,27346,313944,3607664,41448458, 476228082,5471653976,62867030958,722316016670, 8299110691962,95353331221526,1095570130851502, 12587645301298246,144626810987686256, 1661701927233901422] |