The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 3 | 0 |
| 4 | 2 |
| 5 | 10 |
| 6 | 40 |
| 7 | 140 |
| 8 | 462 |
| 9 | 1470 |
| 10 | 4580 |
| 11 | 14080 |
| 12 | 42922 |
| 13 | 130130 |
| 14 | 393120 |
| 15 | 1184820 |
| 16 | 3565382 |
| 17 | 10717990 |
| 18 | 32197660 |
| 19 | 96680360 |
| 20 | 290215842 |
| 21 | 870997050 |
| 22 | 2613690200 |
| 23 | 7842468700 |
| 24 | 23530202302 |
| 25 | 70596199310 |
| 26 | 211799782740 |
| 27 | 635421717840 |
| 28 | 1906309892762 |
| 29 | 5719019156770 |
| 30 | 17157236427280 |
[0,2,10,40,140,462,1470,4580,14080,42922,130130, 393120,1184820,3565382,10717990,32197660,96680360, 290215842,870997050,2613690200,7842468700, 23530202302,70596199310,211799782740,635421717840, 1906309892762,5719019156770,17157236427280] |