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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 64 |
| 4 | 229 |
| 5 | 808 |
| 6 | 2800 |
| 7 | 9472 |
| 8 | 31705 |
| 9 | 105004 |
| 10 | 344416 |
| 11 | 1121920 |
| 12 | 3631645 |
| 13 | 11691472 |
| 14 | 37466656 |
| 15 | 119574784 |
| 16 | 380244721 |
| 17 | 1205309140 |
| 18 | 3809636848 |
| 19 | 12010028224 |
| 20 | 37773505429 |
| 21 | 118550674936 |
| 22 | 371342504848 |
| 23 | 1161099257344 |
| 24 | 3624512382793 |
| 25 | 11297181307900 |
| 26 | 35162477600704 |
[1,4,16,64,229,808,2800,9472,31705,105004,344416, 1121920,3631645,11691472,37466656,119574784, 380244721,1205309140,3809636848,12010028224, 37773505429,118550674936,371342504848, 1161099257344,3624512382793,11297181307900, 35162477600704] |