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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 18 |
| 3 | 204 |
| 4 | 1526 |
| 5 | 15228 |
| 6 | 146676 |
| 7 | 1217880 |
| 8 | 10322982 |
| 9 | 106429420 |
| 10 | 886934236 |
| 11 | 7632390312 |
| 12 | 72137002428 |
| 13 | 600860144728 |
| 14 | 5351962341672 |
| 15 | 51402944345520 |
| 16 | 411439139563526 |
| 17 | 3624067316629836 |
| 18 | 33666668386023244 |
| 19 | 279519776297893512 |
| 20 | 2480351338204454484 |
[1,2,18,204,1526,15228,146676,1217880,10322982, 106429420,886934236,7632390312,72137002428, 600860144728,5351962341672,51402944345520, 411439139563526,3624067316629836, 33666668386023244,279519776297893512, 2480351338204454484] |