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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 24 |
| 3 | 104 |
| 4 | 384 |
| 5 | 1284 |
| 6 | 4012 |
| 7 | 11924 |
| 8 | 34100 |
| 9 | 94584 |
| 10 | 255852 |
| 11 | 677850 |
| 12 | 1764482 |
| 13 | 4523924 |
| 14 | 11447870 |
| 15 | 28636218 |
| 16 | 70907326 |
| 17 | 173991368 |
| 18 | 423469988 |
| 19 | 1023162920 |
| 20 | 2455645268 |
| 21 | 5858183260 |
| 22 | 13898041838 |
| 23 | 32804047708 |
| 24 | 77067740230 |
[0,4,24,104,384,1284,4012,11924,34100,94584, 255852,677850,1764482,4523924,11447870,28636218, 70907326,173991368,423469988,1023162920, 2455645268,5858183260,13898041838,32804047708, 77067740230] |