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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 36 |
| 5 | 96 |
| 6 | 248 |
| 7 | 608 |
| 8 | 1504 |
| 9 | 3648 |
| 10 | 8608 |
| 11 | 19392 |
| 12 | 43712 |
| 13 | 98304 |
| 14 | 222208 |
| 15 | 498560 |
| 16 | 1118784 |
| 17 | 2511872 |
| 18 | 5607296 |
| 19 | 12138496 |
| 20 | 25944960 |
| 21 | 55059456 |
[1,4,12,36,96,248,608,1504,3648,8608,19392,43712, 98304,222208,498560,1118784,2511872,5607296, 12138496,25944960,55059456] |