| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 16 |
| 6 | 39 |
| 7 | 102 |
| 8 | 279 |
| 9 | 782 |
| 10 | 2227 |
| 11 | 6427 |
| 12 | 18769 |
| 13 | 55376 |
| 14 | 164801 |
| 15 | 494071 |
| 16 | 1490663 |
| 17 | 4522690 |
| 18 | 13790171 |
| 19 | 42234621 |
| 20 | 129866725 |
| 21 | 400765128 |
| 22 | 1240796725 |
| 23 | 3853055776 |
| 24 | 11997619209 |
| 25 | 37451945874 |
| 26 | 117181432493 |
| 27 | 367428949069 |
[1,0,1,3,7,16,39,102,279,782,2227,6427,18769, 55376,164801,494071,1490663,4522690,13790171, 42234621,129866725,400765128,1240796725, 3853055776,11997619209,37451945874,117181432493, 367428949069] |