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| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 53 |
| 3 | 121 |
| 4 | 259 |
| 5 | 549 |
| 6 | 1119 |
| 7 | 2285 |
| 8 | 4575 |
| 9 | 9185 |
| 10 | 18275 |
| 11 | 36437 |
| 12 | 72387 |
| 13 | 144013 |
| 14 | 286211 |
| 15 | 569361 |
| 16 | 1132703 |
| 17 | 2254869 |
| 18 | 4490887 |
| 19 | 8948013 |
| 20 | 17838815 |
| 21 | 35573537 |
| 22 | 70976563 |
| 23 | 141639157 |
| 24 | 282775411 |
| 25 | 564615853 |
| 26 | 1127756979 |
| 27 | 2252749969 |
| 28 | 4501187503 |
[21,53,121,259,549,1119,2285,4575,9185,18275, 36437,72387,144013,286211,569361,1132703,2254869, 4490887,8948013,17838815,35573537,70976563, 141639157,282775411,564615853,1127756979, 2252749969,4501187503] |