| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 7 |
| 2 | 56 |
| 3 | 357 |
| 4 | 2464 |
| 5 | 16835 |
| 6 | 118104 |
| 7 | 823585 |
| 8 | 5767328 |
| 9 | 40354335 |
| 10 | 282492280 |
| 11 | 1977326813 |
| 12 | 13841410464 |
| 13 | 96889010491 |
| 14 | 678223896728 |
| 15 | 4747561544985 |
| 16 | 33232936339456 |
| 17 | 232630513987319 |
| 18 | 1628413638500376 |
| 19 | 11398895185373269 |
[0,7,56,357,2464,16835,118104,823585,5767328, 40354335,282492280,1977326813,13841410464, 96889010491,678223896728,4747561544985, 33232936339456,232630513987319,1628413638500376, 11398895185373269] |