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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 17 |
| 3 | 72 |
| 4 | 254 |
| 5 | 1104 |
| 6 | 4428 |
| 7 | 17549 |
| 8 | 71541 |
| 9 | 288624 |
| 10 | 1160216 |
| 11 | 4688893 |
| 12 | 18915890 |
| 13 | 76255262 |
| 14 | 307700021 |
| 15 | 1241251737 |
| 16 | 5006436549 |
| 17 | 20196297041 |
| 18 | 81469428031 |
| 19 | 328628315656 |
| 20 | 1325648873979 |
| 21 | 5347476219467 |
| 22 | 21570824670637 |
| 23 | 87013568475744 |
[4,17,72,254,1104,4428,17549,71541,288624,1160216, 4688893,18915890,76255262,307700021,1241251737, 5006436549,20196297041,81469428031,328628315656, 1325648873979,5347476219467,21570824670637, 87013568475744] |