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| n | a(n) |
|---|---|
| 0 | 4 |
| 1 | 6 |
| 2 | 12 |
| 3 | 30 |
| 4 | 84 |
| 5 | 246 |
| 6 | 732 |
| 7 | 2190 |
| 8 | 6564 |
| 9 | 19686 |
| 10 | 59052 |
| 11 | 177150 |
| 12 | 531444 |
| 13 | 1594326 |
| 14 | 4782972 |
| 15 | 14348910 |
| 16 | 43046724 |
| 17 | 129140166 |
| 18 | 387420492 |
| 19 | 1162261470 |
| 20 | 3486784404 |
| 21 | 10460353206 |
| 22 | 31381059612 |
| 23 | 94143178830 |
| 24 | 282429536484 |
| 25 | 847288609446 |
| 26 | 2541865828332 |
| 27 | 7625597484990 |
[4,6,12,30,84,246,732,2190,6564,19686,59052, 177150,531444,1594326,4782972,14348910,43046724, 129140166,387420492,1162261470,3486784404, 10460353206,31381059612,94143178830,282429536484, 847288609446,2541865828332,7625597484990] |