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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 12 |
| 3 | 40 |
| 4 | 128 |
| 5 | 416 |
| 6 | 1344 |
| 7 | 4352 |
| 8 | 14080 |
| 9 | 45568 |
| 10 | 147456 |
| 11 | 477184 |
| 12 | 1544192 |
| 13 | 4997120 |
| 14 | 16171008 |
| 15 | 52330496 |
| 16 | 169345024 |
| 17 | 548012032 |
| 18 | 1773404160 |
| 19 | 5738856448 |
| 20 | 18571329536 |
| 21 | 60098084864 |
| 22 | 194481487872 |
| 23 | 629355315200 |
| 24 | 2036636581888 |
[1,4,12,40,128,416,1344,4352,14080,45568,147456, 477184,1544192,4997120,16171008,52330496, 169345024,548012032,1773404160,5738856448, 18571329536,60098084864,194481487872,629355315200, 2036636581888] |