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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 67 |
| 4 | 260 |
| 5 | 4741 |
| 6 | 25862 |
| 7 | 350407 |
| 8 | 2330120 |
| 9 | 26735881 |
| 10 | 200269322 |
| 11 | 2084899147 |
| 12 | 16786765580 |
| 13 | 164922177421 |
| 14 | 1387410586382 |
| 15 | 13164918350287 |
| 16 | 113736703642640 |
| 17 | 1056863263353361 |
| 18 | 9279138856193042 |
| 19 | 85140663303647827 |
| 20 | 754867074547457300 |
[1,2,67,260,4741,25862,350407,2330120,26735881, 200269322,2084899147,16786765580,164922177421, 1387410586382,13164918350287,113736703642640, 1056863263353361,9279138856193042, 85140663303647827,754867074547457300] |