| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 12 |
| 5 | 61 |
| 6 | 367 |
| 7 | 2805 |
| 8 | 23372 |
| 9 | 213317 |
| 10 | 2189823 |
| 11 | 24882811 |
| 12 | 305633678 |
| 13 | 4037554628 |
| 14 | 57447084699 |
| 15 | 877263905683 |
| 16 | 14276260437624 |
| 17 | 246201450585329 |
| 18 | 4487236144246511 |
| 19 | 86286209907252739 |
| 20 | 1746559569805617910 |
| 21 | 37106502447954647906 |
| 22 | 825196425771658993531 |
[0,1,2,12,61,367,2805,23372,213317,2189823, 24882811,305633678,4037554628,57447084699, 877263905683,14276260437624,246201450585329, 4487236144246511,86286209907252739, 1746559569805617910,37106502447954647906, 825196425771658993531] |