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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 23 |
| 3 | 152 |
| 4 | 1085 |
| 5 | 8156 |
| 6 | 63579 |
| 7 | 509136 |
| 8 | 4161649 |
| 9 | 34566580 |
| 10 | 290798551 |
| 11 | 2471871784 |
| 12 | 21191824645 |
| 13 | 182984610220 |
| 14 | 1589620392835 |
| 15 | 13881368684128 |
| 16 | 121767703088377 |
| 17 | 1072382299895428 |
| 18 | 9477296423786207 |
| 19 | 84017470425706040 |
| 20 | 746903374745524629 |
| 21 | 6656552616997851036 |
| 22 | 59459592374756968323 |
[1,4,23,152,1085,8156,63579,509136,4161649, 34566580,290798551,2471871784,21191824645, 182984610220,1589620392835,13881368684128, 121767703088377,1072382299895428,9477296423786207, 84017470425706040,746903374745524629, 6656552616997851036,59459592374756968323] |