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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 67 |
| 5 | 633 |
| 6 | 6763 |
| 7 | 77766 |
| 8 | 938957 |
| 9 | 11739033 |
| 10 | 150649945 |
| 11 | 1973059212 |
| 12 | 26265513030 |
| 13 | 354344889798 |
| 14 | 4833929879517 |
| 15 | 66568517557803 |
| 16 | 924166526830701 |
| 17 | 12920482325488761 |
| 18 | 181750521972603049 |
| 19 | 2570566932237176232 |
| 20 | 36532394627404815308 |
| 21 | 521439507533582646156 |
[1,1,2,9,67,633,6763,77766,938957,11739033, 150649945,1973059212,26265513030,354344889798, 4833929879517,66568517557803,924166526830701, 12920482325488761,181750521972603049, 2570566932237176232,36532394627404815308, 521439507533582646156] |