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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 28 |
| 2 | 134 |
| 3 | 502 |
| 4 | 2202 |
| 5 | 9718 |
| 6 | 44000 |
| 7 | 201628 |
| 8 | 933682 |
| 9 | 4357222 |
| 10 | 20462184 |
| 11 | 96587068 |
| 12 | 457871484 |
| 13 | 2178414292 |
| 14 | 10396478562 |
| 15 | 49751026042 |
| 16 | 238639567362 |
| 17 | 1147064158822 |
| 18 | 5523799769432 |
| 19 | 26644582803412 |
| 20 | 128714976934252 |
[1,28,134,502,2202,9718,44000,201628,933682, 4357222,20462184,96587068,457871484,2178414292, 10396478562,49751026042,238639567362, 1147064158822,5523799769432,26644582803412, 128714976934252] |