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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 13 |
| 3 | 42 |
| 4 | 133 |
| 5 | 424 |
| 6 | 1348 |
| 7 | 4291 |
| 8 | 13653 |
| 9 | 43449 |
| 10 | 138261 |
| 11 | 439979 |
| 12 | 1400101 |
| 13 | 4455420 |
| 14 | 14178073 |
| 15 | 45117606 |
| 16 | 143573662 |
| 17 | 456881476 |
| 18 | 1453892534 |
| 19 | 4626590576 |
| 20 | 14722780217 |
| 21 | 46850970327 |
| 22 | 149089600359 |
| 23 | 474434334814 |
| 24 | 1509749422360 |
| 25 | 4804338875098 |
| 26 | 15288412556740 |
[1,4,13,42,133,424,1348,4291,13653,43449,138261, 439979,1400101,4455420,14178073,45117606, 143573662,456881476,1453892534,4626590576, 14722780217,46850970327,149089600359,474434334814, 1509749422360,4804338875098,15288412556740] |