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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 20 |
| 5 | 41 |
| 6 | 104 |
| 7 | 479 |
| 8 | 1146 |
| 9 | 7603 |
| 10 | 16521 |
| 11 | 91146 |
| 12 | 188021 |
| 13 | 188021 |
| 14 | 1861979 |
| 15 | 14122396 |
| 16 | 43294271 |
| 17 | 203450521 |
| 18 | 203450521 |
| 19 | 5877278646 |
| 20 | 5900065104 |
| 21 | 16886393229 |
[1,1,4,20,41,104,479,1146,7603,16521,91146,188021, 188021,1861979,14122396,43294271,203450521, 203450521,5877278646,5900065104,16886393229] |