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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 38 |
| 5 | 111 |
| 6 | 487 |
| 7 | 1613 |
| 8 | 7266 |
| 9 | 25898 |
| 10 | 118756 |
| 11 | 444424 |
| 12 | 2062730 |
| 13 | 7995233 |
| 14 | 37424774 |
| 15 | 148969816 |
| 16 | 701627984 |
| 17 | 2851691801 |
| 18 | 13493743151 |
| 19 | 55771863728 |
| 20 | 264858505725 |
| 21 | 1109897493977 |
| 22 | 5286000156990 |
| 23 | 22407811546785 |
| 24 | 106967054294187 |
| 25 | 457894679334773 |
| 26 | 2189983001429080 |
| 27 | 9453661460869249 |
| 28 | 45285465488383829 |
[1,1,4,9,38,111,487,1613,7266,25898,118756,444424, 2062730,7995233,37424774,148969816,701627984, 2851691801,13493743151,55771863728,264858505725, 1109897493977,5286000156990,22407811546785, 106967054294187,457894679334773,2189983001429080, 9453661460869249,45285465488383829] |