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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 19 |
| 6 | 59 |
| 7 | 179 |
| 8 | 615 |
| 9 | 2141 |
| 10 | 7853 |
| 11 | 30179 |
| 12 | 118663 |
| 13 | 487581 |
| 14 | 2050325 |
| 15 | 8890743 |
| 16 | 39593811 |
| 17 | 180367655 |
| 18 | 842738375 |
| 19 | 4018170415 |
| 20 | 19578229355 |
| 21 | 97275623919 |
| 22 | 492406520567 |
| 23 | 2538806377419 |
| 24 | 13312298342703 |
| 25 | 70986151599775 |
| 26 | 384532625928335 |
| 27 | 2115147900599015 |
[1,1,1,3,7,19,59,179,615,2141,7853,30179,118663, 487581,2050325,8890743,39593811,180367655, 842738375,4018170415,19578229355,97275623919, 492406520567,2538806377419,13312298342703, 70986151599775,384532625928335,2115147900599015] |