| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 2 |
| 5 | 11 |
| 6 | 30 |
| 7 | 84 |
| 8 | 254 |
| 9 | 717 |
| 10 | 1500 |
| 11 | 13035 |
| 12 | 44550 |
| 13 | 300950 |
| 14 | 1505504 |
| 15 | 3854579 |
| 16 | 14283372 |
| 17 | 83480149 |
| 18 | 251709276 |
| 19 | 3136016690 |
| 20 | 12605049160 |
| 21 | 162391467080 |
| 22 | 691231886400 |
| 23 | 3678703702014 |
| 24 | 23362113269002 |
| 25 | 94834621131920 |
| 26 | 374452713892530 |
| 27 | 4019520663745860 |
| 28 | 15252585773825400 |
[1,2,2,2,11,30,84,254,717,1500,13035,44550,300950, 1505504,3854579,14283372,83480149,251709276, 3136016690,12605049160,162391467080,691231886400, 3678703702014,23362113269002,94834621131920, 374452713892530,4019520663745860, 15252585773825400] |