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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 14 |
| 3 | 56 |
| 4 | 226 |
| 5 | 958 |
| 6 | 4052 |
| 7 | 17508 |
| 8 | 75634 |
| 9 | 330804 |
| 10 | 1448830 |
| 11 | 6397288 |
| 12 | 28293338 |
| 13 | 125845174 |
| 14 | 560617586 |
| 15 | 2507890716 |
| 16 | 11234741560 |
| 17 | 50489990570 |
| 18 | 227190742034 |
| 19 | 1024878998006 |
| 20 | 4628430595232 |
[4,14,56,226,958,4052,17508,75634,330804,1448830, 6397288,28293338,125845174,560617586,2507890716, 11234741560,50489990570,227190742034, 1024878998006,4628430595232] |