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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 5 |
| 3 | 25 |
| 4 | 155 |
| 5 | 1025 |
| 6 | 7167 |
| 7 | 51945 |
| 8 | 387000 |
| 9 | 2944860 |
| 10 | 22791189 |
| 11 | 178840639 |
| 12 | 1419569398 |
| 13 | 11377983292 |
| 14 | 91957314063 |
| 15 | 748575327757 |
| 16 | 6132254500856 |
| 17 | 50514620902564 |
| 18 | 418174191239443 |
| 19 | 3477075679541185 |
| 20 | 29026557341147912 |
| 21 | 243184916545458556 |
[1,5,25,155,1025,7167,51945,387000,2944860, 22791189,178840639,1419569398,11377983292, 91957314063,748575327757,6132254500856, 50514620902564,418174191239443,3477075679541185, 29026557341147912,243184916545458556] |