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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 13 |
| 3 | 42 |
| 4 | 141 |
| 5 | 486 |
| 6 | 1685 |
| 7 | 5804 |
| 8 | 19769 |
| 9 | 66544 |
| 10 | 221581 |
| 11 | 730918 |
| 12 | 2391717 |
| 13 | 7772610 |
| 14 | 25110933 |
| 15 | 80713016 |
| 16 | 258280817 |
| 17 | 823269116 |
| 18 | 2615088973 |
| 19 | 8281113730 |
| 20 | 26150883901 |
| 21 | 82375282494 |
| 22 | 258893742933 |
| 23 | 811984918692 |
| 24 | 2541865829801 |
| 25 | 7943330715176 |
[4,13,42,141,486,1685,5804,19769,66544,221581, 730918,2391717,7772610,25110933,80713016, 258280817,823269116,2615088973,8281113730, 26150883901,82375282494,258893742933,811984918692, 2541865829801,7943330715176] |