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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 28 |
| 5 | 86 |
| 6 | 266 |
| 7 | 820 |
| 8 | 2532 |
| 9 | 7812 |
| 10 | 24112 |
| 11 | 74408 |
| 12 | 229640 |
| 13 | 708688 |
| 14 | 2187120 |
| 15 | 6749712 |
| 16 | 20830528 |
| 17 | 64285664 |
| 18 | 198394016 |
| 19 | 612269632 |
| 20 | 1889544000 |
| 21 | 5831378496 |
| 22 | 17996393728 |
| 23 | 55539213440 |
| 24 | 171401244800 |
| 25 | 528966555904 |
| 26 | 1632459664128 |
| 27 | 5037983062272 |
| 28 | 15547871669248 |
[1,3,9,28,86,266,820,2532,7812,24112,74408,229640, 708688,2187120,6749712,20830528,64285664, 198394016,612269632,1889544000,5831378496, 17996393728,55539213440,171401244800,528966555904, 1632459664128,5037983062272,15547871669248] |