| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 24 |
| 3 | 117 |
| 4 | 527 |
| 5 | 3116 |
| 6 | 11753 |
| 7 | 76443 |
| 8 | 354144 |
| 9 | 1721764 |
| 10 | 9653287 |
| 11 | 34867797 |
| 12 | 242017776 |
| 13 | 1064447283 |
| 14 | 5583548873 |
| 15 | 29729597084 |
| 16 | 116749235904 |
| 17 | 761741108157 |
| 18 | 3175197967656 |
| 19 | 17982575014036 |
| 20 | 91004468168113 |
[4,24,117,527,3116,11753,76443,354144,1721764, 9653287,34867797,242017776,1064447283,5583548873, 29729597084,116749235904,761741108157, 3175197967656,17982575014036,91004468168113] |