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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 48 |
| 3 | 264 |
| 4 | 1408 |
| 5 | 7432 |
| 6 | 39152 |
| 7 | 206600 |
| 8 | 1093760 |
| 9 | 5813000 |
| 10 | 31019568 |
| 11 | 166188552 |
| 12 | 893763840 |
| 13 | 4823997960 |
| 14 | 26124870640 |
| 15 | 141926904328 |
| 16 | 773293020928 |
| 17 | 4224773978632 |
| 18 | 23139861329456 |
| 19 | 127039971696392 |
| 20 | 698993630524032 |
| 21 | 3853860616119048 |
| 22 | 21288789223825648 |
[1,8,48,264,1408,7432,39152,206600,1093760, 5813000,31019568,166188552,893763840,4823997960, 26124870640,141926904328,773293020928, 4224773978632,23139861329456,127039971696392, 698993630524032,3853860616119048, 21288789223825648] |