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| n | a(n) |
|---|---|
| 1 | 13 |
| 2 | 57 |
| 3 | 236 |
| 4 | 959 |
| 5 | 3872 |
| 6 | 15586 |
| 7 | 62632 |
| 8 | 251419 |
| 9 | 1008536 |
| 10 | 4043582 |
| 11 | 16206152 |
| 12 | 64933782 |
| 13 | 260114976 |
| 14 | 1041797124 |
| 15 | 4171943056 |
| 16 | 16704821779 |
| 17 | 66880877896 |
| 18 | 267747443494 |
| 19 | 1071808583176 |
| 20 | 4290243456514 |
| 21 | 17172082337536 |
| 22 | 68729504287324 |
[13,57,236,959,3872,15586,62632,251419,1008536, 4043582,16206152,64933782,260114976,1041797124, 4171943056,16704821779,66880877896,267747443494, 1071808583176,4290243456514,17172082337536, 68729504287324] |