The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 2 |
| 10 | 6 |
| 11 | 22 |
| 12 | 67 |
| 13 | 213 |
| 14 | 744 |
| 15 | 2609 |
| 16 | 9016 |
| 17 | 31426 |
| 18 | 110381 |
| 19 | 390223 |
| 20 | 1383905 |
| 21 | 4931307 |
| 22 | 17633765 |
| 23 | 63301415 |
| 24 | 228130900 |
| 25 | 825228950 |
| 26 | 2994833413 |
[0,0,0,0,0,0,0,0,2,6,22,67,213,744,2609,9016, 31426,110381,390223,1383905,4931307,17633765, 63301415,228130900,825228950,2994833413] |