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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 21 |
| 3 | 190 |
| 4 | 1712 |
| 5 | 15411 |
| 6 | 138700 |
| 7 | 1248302 |
| 8 | 11234721 |
| 9 | 101112490 |
| 10 | 910012412 |
| 11 | 8190111711 |
| 12 | 73711005400 |
| 13 | 663399048602 |
| 14 | 5970591437421 |
| 15 | 53735322936790 |
| 16 | 483617906431112 |
| 17 | 4352561157880011 |
| 18 | 39173050420920100 |
| 19 | 352557453788280902 |
| 20 | 3173017084094528121 |
[2,21,190,1712,15411,138700,1248302,11234721, 101112490,910012412,8190111711,73711005400, 663399048602,5970591437421,53735322936790, 483617906431112,4352561157880011, 39173050420920100,352557453788280902, 3173017084094528121] |