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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 59 |
| 6 | 198 |
| 7 | 690 |
| 8 | 2450 |
| 9 | 8878 |
| 10 | 32632 |
| 11 | 121518 |
| 12 | 457262 |
| 13 | 1736526 |
| 14 | 6646340 |
| 15 | 25613086 |
| 16 | 99298674 |
| 17 | 387021728 |
| 18 | 1515594560 |
| 19 | 5960406102 |
| 20 | 23530528512 |
| 21 | 93216984177 |
| 22 | 370450977206 |
| 23 | 1476458287082 |
| 24 | 5900150928510 |
| 25 | 23635544130948 |
[1,1,2,6,18,59,198,690,2450,8878,32632,121518, 457262,1736526,6646340,25613086,99298674, 387021728,1515594560,5960406102,23530528512, 93216984177,370450977206,1476458287082, 5900150928510,23635544130948] |