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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 16 |
| 3 | 50 |
| 4 | 130 |
| 5 | 296 |
| 6 | 624 |
| 7 | 1289 |
| 8 | 2741 |
| 9 | 6134 |
| 10 | 14269 |
| 11 | 33577 |
| 12 | 78304 |
| 13 | 179671 |
| 14 | 406765 |
| 15 | 915275 |
| 16 | 2061311 |
| 17 | 4664237 |
| 18 | 10605587 |
| 19 | 24181837 |
| 20 | 55152622 |
| 21 | 125626530 |
| 22 | 285683099 |
| 23 | 648937238 |
| 24 | 1473615534 |
| 25 | 3347303199 |
| 26 | 7607369029 |
| 27 | 17296530794 |
| 28 | 39333312344 |
[4,16,50,130,296,624,1289,2741,6134,14269,33577, 78304,179671,406765,915275,2061311,4664237, 10605587,24181837,55152622,125626530,285683099, 648937238,1473615534,3347303199,7607369029, 17296530794,39333312344] |