| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 8 |
| 3 | 48 |
| 4 | 242 |
| 5 | 844 |
| 6 | 22020 |
| 7 | 217070 |
| 8 | 1092747 |
| 9 | 8870024 |
| 10 | 262315467 |
| 11 | 221167422 |
| 12 | 47255689915 |
| 13 | 82462576220 |
| 14 | 1043460553364 |
| 15 | 79180770078548 |
| 16 | 3215226335143218 |
| 17 | 23742453640900972 |
| 18 | 125781000834058568 |
[4,8,48,242,844,22020,217070,1092747,8870024, 262315467,221167422,47255689915,82462576220, 1043460553364,79180770078548,3215226335143218, 23742453640900972,125781000834058568] |