| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 2 |
| 6 | 11 |
| 7 | 41 |
| 8 | 136 |
| 9 | 437 |
| 10 | 1397 |
| 11 | 4490 |
| 12 | 14554 |
| 13 | 47683 |
| 14 | 158093 |
| 15 | 530265 |
| 16 | 1797631 |
| 17 | 6153650 |
| 18 | 21252343 |
| 19 | 73986392 |
| 20 | 259434758 |
| 21 | 915667537 |
| 22 | 3251026851 |
| 23 | 11605063370 |
| 24 | 41631062856 |
| 25 | 150021553132 |
| 26 | 542875085143 |
| 27 | 1972049524959 |
[0,0,0,0,2,11,41,136,437,1397,4490,14554,47683, 158093,530265,1797631,6153650,21252343,73986392, 259434758,915667537,3251026851,11605063370, 41631062856,150021553132,542875085143, 1972049524959] |