| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 4 |
| 7 | 16 |
| 8 | 51 |
| 9 | 158 |
| 10 | 463 |
| 11 | 1330 |
| 12 | 3742 |
| 13 | 10438 |
| 14 | 28877 |
| 15 | 79619 |
| 16 | 218997 |
| 17 | 602079 |
| 18 | 1655623 |
| 19 | 4557604 |
| 20 | 12564084 |
| 21 | 34697544 |
| 22 | 96006605 |
| 23 | 266185703 |
| 24 | 739530680 |
| 25 | 2058786037 |
| 26 | 5742859294 |
| 27 | 16050179897 |
| 28 | 44939957405 |
| 29 | 126052336580 |
| 30 | 354158412141 |
[0,0,0,0,1,4,16,51,158,463,1330,3742,10438,28877, 79619,218997,602079,1655623,4557604,12564084, 34697544,96006605,266185703,739530680,2058786037, 5742859294,16050179897,44939957405,126052336580, 354158412141] |