The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 10 |
| 7 | 26 |
| 8 | 68 |
| 9 | 183 |
| 10 | 504 |
| 11 | 1408 |
| 12 | 3982 |
| 13 | 11386 |
| 14 | 32856 |
| 15 | 95551 |
| 16 | 279778 |
| 17 | 824124 |
| 18 | 2440440 |
| 19 | 7260888 |
| 20 | 21694352 |
| 21 | 65066660 |
| 22 | 195825872 |
| 23 | 591217344 |
| 24 | 1790081702 |
| 25 | 5434311914 |
| 26 | 16537576560 |
| 27 | 50439949711 |
| 28 | 154163497958 |
| 29 | 472094359708 |
| 30 | 1448302047274 |
[0,1,0,1,2,4,10,26,68,183,504,1408,3982,11386, 32856,95551,279778,824124,2440440,7260888, 21694352,65066660,195825872,591217344,1790081702, 5434311914,16537576560,50439949711,154163497958, 472094359708,1448302047274] |