| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 21 |
| 6 | 54 |
| 7 | 195 |
| 8 | 573 |
| 9 | 2086 |
| 10 | 6646 |
| 11 | 24289 |
| 12 | 81540 |
| 13 | 299136 |
| 14 | 1040262 |
| 15 | 3832923 |
| 16 | 13660698 |
| 17 | 50572983 |
| 18 | 183450064 |
| 19 | 682447378 |
| 20 | 2507959846 |
| 21 | 9374078232 |
| 22 | 34791088014 |
| 23 | 130624080993 |
| 24 | 488542321116 |
| 25 | 1841890385196 |
| 26 | 6931198308924 |
[1,1,1,3,6,21,54,195,573,2086,6646,24289,81540, 299136,1040262,3832923,13660698,50572983, 183450064,682447378,2507959846,9374078232, 34791088014,130624080993,488542321116, 1841890385196,6931198308924] |