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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 21 |
| 3 | 159 |
| 4 | 1261 |
| 5 | 10268 |
| 6 | 85065 |
| 7 | 713345 |
| 8 | 6036381 |
| 9 | 51438741 |
| 10 | 440780736 |
| 11 | 3794261496 |
| 12 | 32784723361 |
| 13 | 284184613586 |
| 14 | 2470101750095 |
| 15 | 21520640950334 |
| 16 | 187885215032925 |
| 17 | 1643315666085399 |
| 18 | 14396340879235851 |
| 19 | 126302446713155886 |
| 20 | 1109524512806397656 |
[1,3,21,159,1261,10268,85065,713345,6036381, 51438741,440780736,3794261496,32784723361, 284184613586,2470101750095,21520640950334, 187885215032925,1643315666085399, 14396340879235851,126302446713155886, 1109524512806397656] |