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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 2 |
| 6 | 8 |
| 7 | 32 |
| 8 | 120 |
| 9 | 430 |
| 10 | 1508 |
| 11 | 5216 |
| 12 | 17872 |
| 13 | 60866 |
| 14 | 206448 |
| 15 | 698312 |
| 16 | 2357640 |
| 17 | 7949742 |
| 18 | 26782492 |
| 19 | 90175912 |
| 20 | 303496048 |
| 21 | 1021160706 |
| 22 | 3435198296 |
| 23 | 11554530832 |
| 24 | 38860960600 |
| 25 | 130691626574 |
| 26 | 439504634068 |
| 27 | 1477972726608 |
| 28 | 4970048569744 |
[0,0,0,0,2,8,32,120,430,1508,5216,17872,60866, 206448,698312,2357640,7949742,26782492,90175912, 303496048,1021160706,3435198296,11554530832, 38860960600,130691626574,439504634068, 1477972726608,4970048569744] |