The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 6 |
| 3 | 26 |
| 4 | 90 |
| 5 | 302 |
| 6 | 966 |
| 7 | 3026 |
| 8 | 9330 |
| 9 | 28502 |
| 10 | 86526 |
| 11 | 261626 |
| 12 | 788970 |
| 13 | 2375102 |
| 14 | 7141686 |
| 15 | 21457826 |
| 16 | 64439010 |
| 17 | 193448102 |
| 18 | 580606446 |
| 19 | 1742343626 |
| 20 | 5228079450 |
| 21 | 15686335502 |
| 22 | 47063200806 |
| 23 | 141197991026 |
| 24 | 423610750290 |
| 25 | 1270865805302 |
[0,2,6,26,90,302,966,3026,9330,28502,86526,261626, 788970,2375102,7141686,21457826,64439010, 193448102,580606446,1742343626,5228079450, 15686335502,47063200806,141197991026,423610750290, 1270865805302] |