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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 65 |
| 5 | 260 |
| 6 | 1040 |
| 7 | 4161 |
| 8 | 16644 |
| 9 | 66576 |
| 10 | 266305 |
| 11 | 1065220 |
| 12 | 4260880 |
| 13 | 17043521 |
| 14 | 68174084 |
| 15 | 272696336 |
| 16 | 1090785345 |
| 17 | 4363141380 |
| 18 | 17452565520 |
| 19 | 69810262081 |
| 20 | 279241048324 |
| 21 | 1116964193296 |
| 22 | 4467856773185 |
| 23 | 17871427092740 |
| 24 | 71485708370960 |
[1,4,16,65,260,1040,4161,16644,66576,266305, 1065220,4260880,17043521,68174084,272696336, 1090785345,4363141380,17452565520,69810262081, 279241048324,1116964193296,4467856773185, 17871427092740,71485708370960] |