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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 39 |
| 4 | 292 |
| 5 | 2505 |
| 6 | 24306 |
| 7 | 263431 |
| 8 | 3154824 |
| 9 | 41368977 |
| 10 | 589410910 |
| 11 | 9064804551 |
| 12 | 149641946796 |
| 13 | 2638693215769 |
| 14 | 49490245341642 |
| 15 | 983607047803815 |
| 16 | 20646947498718736 |
| 17 | 456392479671188001 |
| 18 | 10595402429677269174 |
| 19 | 257723100178182605287 |
| 20 | 6553958557721713088820 |
[0,1,6,39,292,2505,24306,263431,3154824,41368977, 589410910,9064804551,149641946796,2638693215769, 49490245341642,983607047803815,20646947498718736, 456392479671188001,10595402429677269174, 257723100178182605287,6553958557721713088820] |