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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 8 |
| 5 | 25 |
| 6 | 75 |
| 7 | 245 |
| 8 | 800 |
| 9 | 2700 |
| 10 | 9225 |
| 11 | 32065 |
| 12 | 112632 |
| 13 | 400023 |
| 14 | 1432613 |
| 15 | 5170575 |
| 16 | 18783360 |
| 17 | 68635477 |
| 18 | 252085716 |
| 19 | 930138521 |
| 20 | 3446158600 |
| 21 | 12815663595 |
| 22 | 47820414961 |
| 23 | 178987624513 |
| 24 | 671825020128 |
| 25 | 2528212128750 |
| 26 | 9536894664375 |
| 27 | 36054433807398 |
| 28 | 136583760011496 |
[1,1,1,3,8,25,75,245,800,2700,9225,32065,112632, 400023,1432613,5170575,18783360,68635477, 252085716,930138521,3446158600,12815663595, 47820414961,178987624513,671825020128, 2528212128750,9536894664375,36054433807398, 136583760011496] |