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| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 89 |
| 3 | 353 |
| 4 | 1373 |
| 5 | 5225 |
| 6 | 19645 |
| 7 | 73105 |
| 8 | 270125 |
| 9 | 992545 |
| 10 | 3631741 |
| 11 | 13245457 |
| 12 | 48187085 |
| 13 | 174966209 |
| 14 | 634348221 |
| 15 | 2297224145 |
| 16 | 8311862669 |
| 17 | 30054358337 |
| 18 | 108618731197 |
| 19 | 392419038993 |
| 20 | 1417394738125 |
| 21 | 5118764739265 |
| 22 | 18484320138301 |
| 23 | 66746754619345 |
[21,89,353,1373,5225,19645,73105,270125,992545, 3631741,13245457,48187085,174966209,634348221, 2297224145,8311862669,30054358337,108618731197, 392419038993,1417394738125,5118764739265, 18484320138301,66746754619345] |