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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 18 |
| 3 | 74 |
| 4 | 298 |
| 5 | 1194 |
| 6 | 4778 |
| 7 | 19114 |
| 8 | 76458 |
| 9 | 305834 |
| 10 | 1223338 |
| 11 | 4893354 |
| 12 | 19573418 |
| 13 | 78293674 |
| 14 | 313174698 |
| 15 | 1252698794 |
| 16 | 5010795178 |
| 17 | 20043180714 |
| 18 | 80172722858 |
| 19 | 320690891434 |
| 20 | 1282763565738 |
| 21 | 5131054262954 |
| 22 | 20524217051818 |
| 23 | 82096868207274 |
| 24 | 328387472829098 |
[1,4,18,74,298,1194,4778,19114,76458,305834, 1223338,4893354,19573418,78293674,313174698, 1252698794,5010795178,20043180714,80172722858, 320690891434,1282763565738,5131054262954, 20524217051818,82096868207274,328387472829098] |