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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 21 |
| 3 | 27 |
| 4 | 67 |
| 5 | 139 |
| 6 | 303 |
| 7 | 685 |
| 8 | 1511 |
| 9 | 3316 |
| 10 | 7349 |
| 11 | 16265 |
| 12 | 35899 |
| 13 | 79332 |
| 14 | 175408 |
| 15 | 387618 |
| 16 | 856555 |
| 17 | 1893162 |
| 18 | 4184055 |
| 19 | 9246710 |
| 20 | 20435743 |
| 21 | 45164387 |
| 22 | 99815208 |
| 23 | 220596189 |
| 24 | 487529334 |
| 25 | 1077464178 |
| 26 | 2381248108 |
| 27 | 5262677458 |
| 28 | 11630780579 |
| 29 | 25704601383 |
[4,21,27,67,139,303,685,1511,3316,7349,16265, 35899,79332,175408,387618,856555,1893162,4184055, 9246710,20435743,45164387,99815208,220596189, 487529334,1077464178,2381248108,5262677458, 11630780579,25704601383] |