| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 105 |
| 5 | 606 |
| 6 | 3483 |
| 7 | 19986 |
| 8 | 114609 |
| 9 | 657054 |
| 10 | 3766515 |
| 11 | 21590418 |
| 12 | 123758649 |
| 13 | 709393758 |
| 14 | 4066287627 |
| 15 | 23308182162 |
| 16 | 133603718145 |
| 17 | 765823377054 |
| 18 | 4389738680547 |
| 19 | 25162205542674 |
| 20 | 144231041494281 |
| 21 | 826739659899486 |
| 22 | 4738913739770235 |
| 23 | 27163694339468562 |
[1,3,18,105,606,3483,19986,114609,657054,3766515, 21590418,123758649,709393758,4066287627, 23308182162,133603718145,765823377054, 4389738680547,25162205542674,144231041494281, 826739659899486,4738913739770235, 27163694339468562] |