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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 32 |
| 5 | 125 |
| 6 | 450 |
| 7 | 1715 |
| 8 | 6400 |
| 9 | 24300 |
| 10 | 92250 |
| 11 | 352715 |
| 12 | 1351584 |
| 13 | 5200299 |
| 14 | 20056582 |
| 15 | 77558625 |
| 16 | 300533760 |
| 17 | 1166803109 |
| 18 | 4537542888 |
| 19 | 17672631899 |
| 20 | 68923172000 |
| 21 | 269128935495 |
| 22 | 1052049129142 |
| 23 | 4116715363799 |
| 24 | 16123800483072 |
[1,1,2,9,32,125,450,1715,6400,24300,92250,352715, 1351584,5200299,20056582,77558625,300533760, 1166803109,4537542888,17672631899,68923172000, 269128935495,1052049129142,4116715363799, 16123800483072] |