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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 8 |
| 6 | 38 |
| 7 | 326 |
| 8 | 2160 |
| 9 | 14092 |
| 10 | 119776 |
| 11 | 1726772 |
| 12 | 17087084 |
| 13 | 202819128 |
| 14 | 2671905592 |
| 15 | 43460010864 |
| 16 | 653865234996 |
| 17 | 10669423514948 |
| 18 | 193608386667944 |
| 19 | 3712432320889004 |
| 20 | 73424512657548576 |
[1,1,1,4,8,38,326,2160,14092,119776,1726772, 17087084,202819128,2671905592,43460010864, 653865234996,10669423514948,193608386667944, 3712432320889004,73424512657548576] |