| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 9 |
| 4 | 30 |
| 5 | 90 |
| 6 | 255 |
| 7 | 693 |
| 8 | 1820 |
| 9 | 4644 |
| 10 | 11565 |
| 11 | 28215 |
| 12 | 67650 |
| 13 | 159822 |
| 14 | 372827 |
| 15 | 860265 |
| 16 | 1966200 |
| 17 | 4456584 |
| 18 | 10027161 |
| 19 | 22413483 |
| 20 | 49807550 |
| 21 | 110100690 |
| 22 | 242221287 |
| 23 | 530579709 |
| 24 | 1157628180 |
| 25 | 2516582700 |
| 26 | 5452595525 |
| 27 | 11777605983 |
| 28 | 25367150970 |
| 29 | 54492397974 |
| 30 | 116769423795 |
[2,9,30,90,255,693,1820,4644,11565,28215,67650, 159822,372827,860265,1966200,4456584,10027161, 22413483,49807550,110100690,242221287,530579709, 1157628180,2516582700,5452595525,11777605983, 25367150970,54492397974,116769423795] |