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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 25 |
| 4 | 81 |
| 5 | 241 |
| 6 | 673 |
| 7 | 1793 |
| 8 | 4609 |
| 9 | 11521 |
| 10 | 28161 |
| 11 | 67585 |
| 12 | 159745 |
| 13 | 372737 |
| 14 | 860161 |
| 15 | 1966081 |
| 16 | 4456449 |
| 17 | 10027009 |
| 18 | 22413313 |
| 19 | 49807361 |
| 20 | 110100481 |
| 21 | 242221057 |
| 22 | 530579457 |
| 23 | 1157627905 |
| 24 | 2516582401 |
| 25 | 5452595201 |
| 26 | 11777605633 |
| 27 | 25367150593 |
| 28 | 54492397569 |
| 29 | 116769423361 |
[1,2,7,25,81,241,673,1793,4609,11521,28161,67585, 159745,372737,860161,1966081,4456449,10027009, 22413313,49807361,110100481,242221057,530579457, 1157627905,2516582401,5452595201,11777605633, 25367150593,54492397569,116769423361] |