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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 12 |
| 3 | 34 |
| 4 | 108 |
| 5 | 344 |
| 6 | 1104 |
| 7 | 3546 |
| 8 | 11396 |
| 9 | 36628 |
| 10 | 117732 |
| 11 | 378426 |
| 12 | 1216380 |
| 13 | 3909832 |
| 14 | 12567448 |
| 15 | 40395794 |
| 16 | 129844996 |
| 17 | 417363332 |
| 18 | 1341539196 |
| 19 | 4312135922 |
| 20 | 13860583628 |
| 21 | 44552347608 |
| 22 | 143205490528 |
| 23 | 460308235562 |
| 24 | 1479577849604 |
[0,4,12,34,108,344,1104,3546,11396,36628,117732, 378426,1216380,3909832,12567448,40395794, 129844996,417363332,1341539196,4312135922, 13860583628,44552347608,143205490528,460308235562, 1479577849604] |