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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 40 |
| 5 | 121 |
| 6 | 364 |
| 7 | 1093 |
| 8 | 3280 |
| 9 | 9841 |
| 10 | 29524 |
| 11 | 88573 |
| 12 | 265720 |
| 13 | 797161 |
| 14 | 2391484 |
| 15 | 7174453 |
| 16 | 21523360 |
| 17 | 64570081 |
| 18 | 193710244 |
| 19 | 581130733 |
| 20 | 1743392200 |
| 21 | 5230176601 |
| 22 | 15690529804 |
| 23 | 47071589413 |
| 24 | 141214768240 |
| 25 | 423644304721 |
| 26 | 1270932914164 |
[0,1,4,13,40,121,364,1093,3280,9841,29524,88573, 265720,797161,2391484,7174453,21523360,64570081, 193710244,581130733,1743392200,5230176601, 15690529804,47071589413,141214768240,423644304721, 1270932914164] |