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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 38 |
| 5 | 118 |
| 6 | 498 |
| 7 | 1693 |
| 8 | 7476 |
| 9 | 27274 |
| 10 | 121508 |
| 11 | 459786 |
| 12 | 2088146 |
| 13 | 8159974 |
| 14 | 37273054 |
| 15 | 148506527 |
| 16 | 685469238 |
| 17 | 2782946570 |
| 18 | 12891587770 |
| 19 | 52985836682 |
| 20 | 247036106682 |
| 21 | 1027949193490 |
| 22 | 4804382145816 |
| 23 | 20163657925260 |
| 24 | 94647795901516 |
| 25 | 400712095605404 |
| 26 | 1884314609352340 |
| 27 | 8028421804207614 |
| 28 | 37869092843852154 |
[1,1,4,9,38,118,498,1693,7476,27274,121508,459786, 2088146,8159974,37273054,148506527,685469238, 2782946570,12891587770,52985836682,247036106682, 1027949193490,4804382145816,20163657925260, 94647795901516,400712095605404,1884314609352340, 8028421804207614,37869092843852154] |