| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 19 |
| 5 | 55 |
| 6 | 159 |
| 7 | 471 |
| 8 | 1403 |
| 9 | 4199 |
| 10 | 12583 |
| 11 | 37735 |
| 12 | 113187 |
| 13 | 339543 |
| 14 | 1018607 |
| 15 | 3055799 |
| 16 | 9167371 |
| 17 | 27502087 |
| 18 | 82506231 |
| 19 | 247518663 |
| 20 | 742555955 |
| 21 | 2227667831 |
| 22 | 6683003455 |
| 23 | 20049010327 |
| 24 | 60147030939 |
| 25 | 180441092775 |
| 26 | 541323278279 |
| 27 | 1623969834791 |
| 28 | 4871909504323 |
[0,1,3,7,19,55,159,471,1403,4199,12583,37735, 113187,339543,1018607,3055799,9167371,27502087, 82506231,247518663,742555955,2227667831, 6683003455,20049010327,60147030939,180441092775, 541323278279,1623969834791,4871909504323] |