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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 | 236190 |
| 12 | 708552 |
| 13 | 2125608 |
| 14 | 6376680 |
| 15 | 19129608 |
| 16 | 57387528 |
| 17 | 172158696 |
| 18 | 516464424 |
| 19 | 1549358280 |
| 20 | 4647969864 |
| 21 | 13943594664 |
| 22 | 41829839238 |
| 23 | 125486683524 |
| 24 | 376451548188 |
| 25 | 1129329137988 |
[1,4,12,36,108,324,972,2916,8748,26244,78732, 236190,708552,2125608,6376680,19129608,57387528, 172158696,516464424,1549358280,4647969864, 13943594664,41829839238,125486683524,376451548188, 1129329137988] |