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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 25 |
| 6 | 78 |
| 7 | 256 |
| 8 | 881 |
| 9 | 3064 |
| 10 | 10831 |
| 11 | 38766 |
| 12 | 140550 |
| 13 | 514625 |
| 14 | 1900301 |
| 15 | 7067013 |
| 16 | 26448613 |
| 17 | 99539716 |
| 18 | 376489459 |
| 19 | 1430330451 |
| 20 | 5455742957 |
| 21 | 20885223619 |
| 22 | 80213926069 |
| 23 | 309002022843 |
| 24 | 1193616950854 |
| 25 | 4622372591972 |
| 26 | 17942238661229 |
| 27 | 69795082381496 |
| 28 | 272046051362013 |
[1,0,1,3,9,25,78,256,881,3064,10831,38766,140550, 514625,1900301,7067013,26448613,99539716, 376489459,1430330451,5455742957,20885223619, 80213926069,309002022843,1193616950854, 4622372591972,17942238661229,69795082381496, 272046051362013] |