The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 8 |
| 5 | 24 |
| 6 | 88 |
| 7 | 284 |
| 8 | 772 |
| 9 | 2000 |
| 10 | 5008 |
| 11 | 12060 |
| 12 | 28300 |
| 13 | 65192 |
| 14 | 147736 |
| 15 | 330340 |
| 16 | 730740 |
| 17 | 1601744 |
| 18 | 3483616 |
| 19 | 7526252 |
| 20 | 16167132 |
| 21 | 34555192 |
| 22 | 73534440 |
| 23 | 155880628 |
| 24 | 329312132 |
| 25 | 693584736 |
| 26 | 1456820784 |
| 27 | 3052436156 |
| 28 | 6381514348 |
| 29 | 13314563144 |
| 30 | 27728987832 |
[1,0,0,8,24,88,284,772,2000,5008,12060,28300, 65192,147736,330340,730740,1601744,3483616, 7526252,16167132,34555192,73534440,155880628, 329312132,693584736,1456820784,3052436156, 6381514348,13314563144,27728987832] |