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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 15 |
| 2 | 128 |
| 3 | 815 |
| 4 | 4289 |
| 5 | 19663 |
| 6 | 81057 |
| 7 | 306799 |
| 8 | 1081986 |
| 9 | 3594142 |
| 10 | 11338690 |
| 11 | 34193246 |
| 12 | 99080387 |
| 13 | 277046893 |
| 14 | 750192227 |
| 15 | 1973050940 |
| 16 | 5053026949 |
| 17 | 12628736331 |
| 18 | 30859262181 |
| 19 | 73849589786 |
| 20 | 173333118663 |
| 21 | 399528823032 |
| 22 | 905418038792 |
| 23 | 2019454523623 |
| 24 | 4437187104779 |
[1,15,128,815,4289,19663,81057,306799,1081986, 3594142,11338690,34193246,99080387,277046893, 750192227,1973050940,5053026949,12628736331, 30859262181,73849589786,173333118663,399528823032, 905418038792,2019454523623,4437187104779] |