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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 27 |
| 4 | 78 |
| 5 | 228 |
| 6 | 666 |
| 7 | 1944 |
| 8 | 5676 |
| 9 | 16572 |
| 10 | 48384 |
| 11 | 141264 |
| 12 | 412440 |
| 13 | 1204176 |
| 14 | 3515760 |
| 15 | 10264752 |
| 16 | 29969376 |
| 17 | 87499776 |
| 18 | 255467808 |
| 19 | 745873920 |
| 20 | 2177683008 |
| 21 | 6358049472 |
| 22 | 18563212800 |
| 23 | 54197890560 |
| 24 | 158238305664 |
| 25 | 461998818048 |
| 26 | 1348870028544 |
| 27 | 3938214304512 |
[1,3,9,27,78,228,666,1944,5676,16572,48384,141264, 412440,1204176,3515760,10264752,29969376,87499776, 255467808,745873920,2177683008,6358049472, 18563212800,54197890560,158238305664,461998818048, 1348870028544,3938214304512] |