| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 40 |
| 4 | 206 |
| 5 | 1084 |
| 6 | 5802 |
| 7 | 31440 |
| 8 | 171946 |
| 9 | 947132 |
| 10 | 5247010 |
| 11 | 29203928 |
| 12 | 163176586 |
| 13 | 914744612 |
| 14 | 5142354178 |
| 15 | 28978786976 |
| 16 | 163652047834 |
| 17 | 925925993132 |
| 18 | 5247514156418 |
| 19 | 29783577676840 |
| 20 | 169270380108906 |
| 21 | 963186164033652 |
[1,2,8,40,206,1084,5802,31440,171946,947132, 5247010,29203928,163176586,914744612,5142354178, 28978786976,163652047834,925925993132, 5247514156418,29783577676840,169270380108906, 963186164033652] |