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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 138 |
| 3 | 2292 |
| 4 | 47046 |
| 5 | 852756 |
| 6 | 18266628 |
| 7 | 366635112 |
| 8 | 7948637382 |
| 9 | 170568754692 |
| 10 | 3761729402412 |
| 11 | 83136335360856 |
| 12 | 1863229219846428 |
| 13 | 41883396293989320 |
| 14 | 948524060727094728 |
| 15 | 21555960625992644304 |
| 16 | 492036151405623971142 |
| 17 | 11264431786398948383844 |
| 18 | 258676355450246122857756 |
[1,6,138,2292,47046,852756,18266628,366635112, 7948637382,170568754692,3761729402412, 83136335360856,1863229219846428,41883396293989320, 948524060727094728,21555960625992644304, 492036151405623971142,11264431786398948383844, 258676355450246122857756] |