The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 16 |
| 6 | 44 |
| 7 | 130 |
| 8 | 402 |
| 9 | 1302 |
| 10 | 4413 |
| 11 | 15569 |
| 12 | 57025 |
| 13 | 216348 |
| 14 | 848276 |
| 15 | 3430608 |
| 16 | 14285534 |
| 17 | 61155157 |
| 18 | 268761742 |
| 19 | 1210999692 |
| 20 | 5588016550 |
| 21 | 26378327264 |
| 22 | 127259503463 |
| 23 | 626899847777 |
| 24 | 3150741885292 |
| 25 | 16143690587631 |
| 26 | 84267627864828 |
| 27 | 447817207758155 |
| 28 | 2421343092445682 |
[0,0,1,2,6,16,44,130,402,1302,4413,15569,57025, 216348,848276,3430608,14285534,61155157,268761742, 1210999692,5588016550,26378327264,127259503463, 626899847777,3150741885292,16143690587631, 84267627864828,447817207758155,2421343092445682] |