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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 9 |
| 3 | 27 |
| 4 | 81 |
| 5 | 243 |
| 6 | 704 |
| 7 | 1664 |
| 8 | 3840 |
| 9 | 8704 |
| 10 | 19456 |
| 11 | 43008 |
| 12 | 94208 |
| 13 | 204800 |
| 14 | 442368 |
| 15 | 950272 |
| 16 | 2031616 |
| 17 | 4325376 |
| 18 | 9175040 |
| 19 | 19398656 |
| 20 | 40894464 |
| 21 | 85983232 |
| 22 | 180355072 |
| 23 | 377487360 |
| 24 | 788529152 |
| 25 | 1644167168 |
| 26 | 3422552064 |
| 27 | 7113539584 |
| 28 | 14763950080 |
[2,9,27,81,243,704,1664,3840,8704,19456,43008, 94208,204800,442368,950272,2031616,4325376, 9175040,19398656,40894464,85983232,180355072, 377487360,788529152,1644167168,3422552064, 7113539584,14763950080] |