| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 2 |
| 3 | 16 |
| 4 | 68 |
| 5 | 304 |
| 6 | 1352 |
| 7 | 6016 |
| 8 | 26768 |
| 9 | 119104 |
| 10 | 529952 |
| 11 | 2358016 |
| 12 | 10491968 |
| 13 | 46683904 |
| 14 | 207719552 |
| 15 | 924246016 |
| 16 | 4112423168 |
| 17 | 18298184704 |
| 18 | 81417585152 |
| 19 | 362266710016 |
| 20 | 1611902010368 |
| 21 | 7172141461504 |
| 22 | 31912369866752 |
| 23 | 141993762390016 |
| 24 | 631799789293568 |
| 25 | 2811186681954304 |
[4,2,16,68,304,1352,6016,26768,119104,529952, 2358016,10491968,46683904,207719552,924246016, 4112423168,18298184704,81417585152,362266710016, 1611902010368,7172141461504,31912369866752, 141993762390016,631799789293568,2811186681954304] |