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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 9 |
| 2 | 55 |
| 3 | 285 |
| 4 | 1351 |
| 5 | 6069 |
| 6 | 26335 |
| 7 | 111645 |
| 8 | 465751 |
| 9 | 1921029 |
| 10 | 7859215 |
| 11 | 31964205 |
| 12 | 129442951 |
| 13 | 522538389 |
| 14 | 2104469695 |
| 15 | 8460859965 |
| 16 | 33972448951 |
| 17 | 136276954149 |
| 18 | 546269553775 |
| 19 | 2188563950925 |
| 20 | 8764714059751 |
| 21 | 35090233104309 |
| 22 | 140455067207455 |
| 23 | 562102681589085 |
| 24 | 2249257981411351 |
[1,9,55,285,1351,6069,26335,111645,465751,1921029, 7859215,31964205,129442951,522538389,2104469695, 8460859965,33972448951,136276954149,546269553775, 2188563950925,8764714059751,35090233104309, 140455067207455,562102681589085,2249257981411351] |