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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 38 |
| 5 | 78 |
| 6 | 160 |
| 7 | 316 |
| 8 | 644 |
| 9 | 1296 |
| 10 | 2578 |
| 11 | 5186 |
| 12 | 10368 |
| 13 | 20744 |
| 14 | 41532 |
| 15 | 83076 |
| 16 | 166172 |
| 17 | 332364 |
| 18 | 664864 |
| 19 | 1329768 |
| 20 | 2659656 |
| 21 | 5319504 |
[2,2,6,20,38,78,160,316,644,1296,2578,5186,10368, 20744,41532,83076,166172,332364,664864,1329768, 2659656,5319504] |