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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 57 |
| 6 | 310 |
| 7 | 1508 |
| 8 | 6854 |
| 9 | 29487 |
| 10 | 122326 |
| 11 | 493459 |
| 12 | 1947088 |
| 13 | 7547120 |
| 14 | 28825124 |
| 15 | 108734941 |
| 16 | 405846502 |
| 17 | 1500971233 |
| 18 | 5506856450 |
| 19 | 20061712660 |
| 20 | 72628513234 |
| 21 | 261461893675 |
| 22 | 936516327062 |
| 23 | 3339154281263 |
| 24 | 11856367499652 |
| 25 | 41938909254744 |
[0,0,1,6,57,310,1508,6854,29487,122326,493459, 1947088,7547120,28825124,108734941,405846502, 1500971233,5506856450,20061712660,72628513234, 261461893675,936516327062,3339154281263, 11856367499652,41938909254744] |