| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 28 |
| 2 | 756 |
| 3 | 20412 |
| 4 | 551124 |
| 5 | 14880348 |
| 6 | 401769018 |
| 7 | 10847753280 |
| 8 | 292889063376 |
| 9 | 7907997281184 |
| 10 | 213515725982832 |
| 11 | 5764919185089792 |
| 12 | 155652671753506746 |
| 13 | 4202618188762620900 |
| 14 | 113470584484975272828 |
| 15 | 3063702902583418604964 |
[1,28,756,20412,551124,14880348,401769018, 10847753280,292889063376,7907997281184, 213515725982832,5764919185089792, 155652671753506746,4202618188762620900, 113470584484975272828,3063702902583418604964] |