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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 46 |
| 4 | 330 |
| 5 | 2778 |
| 6 | 24094 |
| 7 | 219318 |
| 8 | 2048274 |
| 9 | 19583410 |
| 10 | 190497142 |
| 11 | 1880184446 |
| 12 | 18778814938 |
| 13 | 189456108554 |
| 14 | 1927852050830 |
| 15 | 19763367194630 |
| 16 | 203919590002210 |
| 17 | 2116079501498722 |
| 18 | 22069907395614182 |
| 19 | 231222485352688590 |
| 20 | 2432325883912444010 |
[1,2,6,46,330,2778,24094,219318,2048274,19583410, 190497142,1880184446,18778814938,189456108554, 1927852050830,19763367194630,203919590002210, 2116079501498722,22069907395614182, 231222485352688590,2432325883912444010] |