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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 12 |
| 4 | 38 |
| 5 | 116 |
| 6 | 360 |
| 7 | 1144 |
| 8 | 3670 |
| 9 | 11836 |
| 10 | 38392 |
| 11 | 125160 |
| 12 | 409628 |
| 13 | 1345000 |
| 14 | 4428752 |
| 15 | 14618608 |
| 16 | 48356838 |
| 17 | 160260332 |
| 18 | 532009688 |
| 19 | 1768729736 |
| 20 | 5888250996 |
| 21 | 19626282328 |
| 22 | 65489004464 |
| 23 | 218743627408 |
| 24 | 731311554044 |
| 25 | 2447018357208 |
| 26 | 8194289368240 |
| 27 | 27459924376592 |
[1,2,4,12,38,116,360,1144,3670,11836,38392,125160, 409628,1345000,4428752,14618608,48356838, 160260332,532009688,1768729736,5888250996, 19626282328,65489004464,218743627408,731311554044, 2447018357208,8194289368240,27459924376592] |