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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 15 |
| 5 | 50 |
| 6 | 186 |
| 7 | 834 |
| 8 | 4243 |
| 9 | 24318 |
| 10 | 154780 |
| 11 | 1083952 |
| 12 | 8280624 |
| 13 | 68531308 |
| 14 | 610796150 |
| 15 | 5832677415 |
| 16 | 59411150931 |
| 17 | 642979374958 |
| 18 | 7368000716808 |
| 19 | 89121684577460 |
| 20 | 1134732527849730 |
| 21 | 15170256449030866 |
| 22 | 212469074496520610 |
| 23 | 3111026318662704255 |
| 24 | 47532980801984327584 |
[0,1,3,6,15,50,186,834,4243,24318,154780,1083952, 8280624,68531308,610796150,5832677415,59411150931, 642979374958,7368000716808,89121684577460, 1134732527849730,15170256449030866, 212469074496520610,3111026318662704255, 47532980801984327584] |