| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 3 |
| 3 | 6 |
| 4 | 21 |
| 5 | 78 |
| 6 | 318 |
| 7 | 1356 |
| 8 | 5997 |
| 9 | 27222 |
| 10 | 126138 |
| 11 | 594132 |
| 12 | 2836290 |
| 13 | 13692300 |
| 14 | 66729180 |
| 15 | 327855768 |
| 16 | 1622216829 |
| 17 | 8076311142 |
| 18 | 40427919714 |
| 19 | 203353800324 |
| 20 | 1027318915254 |
| 21 | 5210182030308 |
| 22 | 26517609163812 |
| 23 | 135397544040744 |
| 24 | 693364054299474 |
[2,3,6,21,78,318,1356,5997,27222,126138,594132, 2836290,13692300,66729180,327855768,1622216829, 8076311142,40427919714,203353800324,1027318915254, 5210182030308,26517609163812,135397544040744, 693364054299474] |