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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 52 |
| 3 | 312 |
| 4 | 1802 |
| 5 | 10200 |
| 6 | 57092 |
| 7 | 317544 |
| 8 | 1760035 |
| 9 | 9738160 |
| 10 | 53844184 |
| 11 | 297717712 |
| 12 | 1646893140 |
| 13 | 9116815952 |
| 14 | 50514367512 |
| 15 | 280173703472 |
| 16 | 1555632093093 |
| 17 | 8647009926904 |
| 18 | 48117998453036 |
| 19 | 268057662257096 |
| 20 | 1494927614877214 |
[1,8,52,312,1802,10200,57092,317544,1760035, 9738160,53844184,297717712,1646893140,9116815952, 50514367512,280173703472,1555632093093, 8647009926904,48117998453036,268057662257096, 1494927614877214] |