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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 1 |
| 6 | 3 |
| 7 | 9 |
| 8 | 29 |
| 9 | 98 |
| 10 | 350 |
| 11 | 1302 |
| 12 | 5062 |
| 13 | 20380 |
| 14 | 85108 |
| 15 | 366444 |
| 16 | 1627836 |
| 17 | 7430360 |
| 18 | 34855016 |
| 19 | 167546408 |
| 20 | 825185448 |
| 21 | 4155400720 |
| 22 | 21388745008 |
| 23 | 112355110672 |
| 24 | 602103194448 |
| 25 | 3287743832352 |
| 26 | 18285157048544 |
| 27 | 103480813034336 |
| 28 | 595671084096608 |
| 29 | 3485006638408128 |
[0,0,0,0,1,1,3,9,29,98,350,1302,5062,20380,85108, 366444,1627836,7430360,34855016,167546408, 825185448,4155400720,21388745008,112355110672, 602103194448,3287743832352,18285157048544, 103480813034336,595671084096608,3485006638408128] |