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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 13 |
| 3 | 55 |
| 4 | 233 |
| 5 | 971 |
| 6 | 3981 |
| 7 | 16143 |
| 8 | 65041 |
| 9 | 261139 |
| 10 | 1046549 |
| 11 | 4190231 |
| 12 | 16769049 |
| 13 | 67092507 |
| 14 | 268402717 |
| 15 | 1073676319 |
| 16 | 4294836257 |
| 17 | 17179607075 |
| 18 | 68718952485 |
| 19 | 274876858407 |
| 20 | 1099509530665 |
| 21 | 4398042316843 |
| 22 | 17592177655853 |
| 23 | 70368727400495 |
| 24 | 281474943156273 |
| 25 | 1125899839733811 |
[3,13,55,233,971,3981,16143,65041,261139,1046549, 4190231,16769049,67092507,268402717,1073676319, 4294836257,17179607075,68718952485,274876858407, 1099509530665,4398042316843,17592177655853, 70368727400495,281474943156273,1125899839733811] |