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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 13 |
| 5 | 43 |
| 6 | 179 |
| 7 | 754 |
| 8 | 3752 |
| 9 | 18910 |
| 10 | 107947 |
| 11 | 626797 |
| 12 | 4007984 |
| 13 | 26177428 |
| 14 | 184572504 |
| 15 | 1333510143 |
| 16 | 10251720776 |
| 17 | 80925610461 |
| 18 | 672581036971 |
| 19 | 5745786626079 |
| 20 | 51276472540865 |
| 21 | 470474128209758 |
| 22 | 4483074757033617 |
| 23 | 43904371855787890 |
[1,2,4,13,43,179,754,3752,18910,107947,626797, 4007984,26177428,184572504,1333510143,10251720776, 80925610461,672581036971,5745786626079, 51276472540865,470474128209758,4483074757033617, 43904371855787890] |