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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 2 |
| 3 | 18 |
| 4 | 8 |
| 5 | 44 |
| 6 | 56 |
| 7 | 140 |
| 8 | 364 |
| 9 | 764 |
| 10 | 2352 |
| 11 | 5612 |
| 12 | 16144 |
| 13 | 42324 |
| 14 | 116260 |
| 15 | 314408 |
| 16 | 853216 |
| 17 | 2319700 |
| 18 | 6290064 |
| 19 | 17095288 |
| 20 | 46394920 |
| 21 | 126019004 |
| 22 | 342168972 |
| 23 | 929215108 |
| 24 | 2523394628 |
| 25 | 6852508984 |
| 26 | 18609263140 |
| 27 | 50535852808 |
| 28 | 137239321084 |
| 29 | 372695225548 |
[4,2,18,8,44,56,140,364,764,2352,5612,16144,42324, 116260,314408,853216,2319700,6290064,17095288, 46394920,126019004,342168972,929215108,2523394628, 6852508984,18609263140,50535852808,137239321084, 372695225548] |