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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 9 |
| 5 | 55 |
| 6 | 117 |
| 7 | 775 |
| 8 | 1785 |
| 9 | 12350 |
| 10 | 29799 |
| 11 | 211876 |
| 12 | 527085 |
| 13 | 3818430 |
| 14 | 9706503 |
| 15 | 71282640 |
| 16 | 184138713 |
| 17 | 1366368375 |
| 18 | 3573805950 |
| 19 | 26735839650 |
| 20 | 70625252863 |
| 21 | 531838637759 |
| 22 | 1416298046436 |
| 23 | 10723307329700 |
| 24 | 28748759731965 |
| 25 | 218658647805780 |
| 26 | 589546754316126 |
| 27 | 4501362056183300 |
[1,1,1,5,9,55,117,775,1785,12350,29799,211876, 527085,3818430,9706503,71282640,184138713, 1366368375,3573805950,26735839650,70625252863, 531838637759,1416298046436,10723307329700, 28748759731965,218658647805780,589546754316126, 4501362056183300] |