| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 3 |
| 2 | 22 |
| 3 | 126 |
| 4 | 652 |
| 5 | 3190 |
| 6 | 15060 |
| 7 | 69356 |
| 8 | 313624 |
| 9 | 1398438 |
| 10 | 6166660 |
| 11 | 26948548 |
| 12 | 116888232 |
| 13 | 503811516 |
| 14 | 2159864392 |
| 15 | 9216445080 |
| 16 | 39168381488 |
| 17 | 165864540934 |
| 18 | 700151508324 |
| 19 | 2947120122068 |
| 20 | 12373581565960 |
| 21 | 51831196048212 |
| 22 | 216659135089496 |
| 23 | 903925011410536 |
[0,3,22,126,652,3190,15060,69356,313624,1398438, 6166660,26948548,116888232,503811516,2159864392, 9216445080,39168381488,165864540934,700151508324, 2947120122068,12373581565960,51831196048212, 216659135089496,903925011410536] |