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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 40 |
| 6 | 136 |
| 7 | 429 |
| 8 | 1544 |
| 9 | 5686 |
| 10 | 22265 |
| 11 | 90714 |
| 12 | 386298 |
| 13 | 1705828 |
| 14 | 7806446 |
| 15 | 36899178 |
| 16 | 179843447 |
| 17 | 902128265 |
| 18 | 4650549252 |
| 19 | 24604524692 |
| 20 | 133442382601 |
| 21 | 741107102344 |
| 22 | 4210787843737 |
| 23 | 24454774814641 |
| 24 | 145056183186691 |
| 25 | 878136807089527 |
[1,0,2,5,15,40,136,429,1544,5686,22265,90714, 386298,1705828,7806446,36899178,179843447, 902128265,4650549252,24604524692,133442382601, 741107102344,4210787843737,24454774814641, 145056183186691,878136807089527] |