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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 12 |
| 6 | 11 |
| 7 | 30 |
| 8 | 120 |
| 9 | 252 |
| 10 | 408 |
| 11 | 1104 |
| 12 | 3415 |
| 13 | 7710 |
| 14 | 15984 |
| 15 | 42609 |
| 16 | 118422 |
| 17 | 281820 |
| 18 | 657468 |
| 19 | 1732008 |
| 20 | 4608288 |
| 21 | 11375240 |
| 22 | 28100400 |
| 23 | 73598112 |
| 24 | 192776895 |
| 25 | 487507038 |
| 26 | 1239516384 |
| 27 | 3241480275 |
| 28 | 8460205842 |
| 29 | 21733941060 |
| 30 | 56121723411 |
| 31 | 146904032622 |
| 32 | 383900676120 |
[1,2,0,1,6,12,11,30,120,252,408,1104,3415,7710, 15984,42609,118422,281820,657468,1732008,4608288, 11375240,28100400,73598112,192776895,487507038, 1239516384,3241480275,8460205842,21733941060, 56121723411,146904032622,383900676120] |