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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 12 |
| 3 | 36 |
| 4 | 108 |
| 5 | 324 |
| 6 | 972 |
| 7 | 2916 |
| 8 | 8748 |
| 9 | 26244 |
| 10 | 78732 |
| 11 | 236196 |
| 12 | 708588 |
| 13 | 2125764 |
| 14 | 6377292 |
| 15 | 19131876 |
| 16 | 57395628 |
| 17 | 172186878 |
| 18 | 516560616 |
| 19 | 1549681800 |
| 20 | 4649045256 |
| 21 | 13947135336 |
| 22 | 41841404712 |
| 23 | 125524210248 |
| 24 | 376572619080 |
| 25 | 1129717822248 |
[1,4,12,36,108,324,972,2916,8748,26244,78732, 236196,708588,2125764,6377292,19131876,57395628, 172186878,516560616,1549681800,4649045256, 13947135336,41841404712,125524210248,376572619080, 1129717822248] |