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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 52 |
| 3 | 395 |
| 4 | 3036 |
| 5 | 23506 |
| 6 | 182904 |
| 7 | 1428387 |
| 8 | 11185900 |
| 9 | 87789702 |
| 10 | 690212744 |
| 11 | 5434455182 |
| 12 | 42841215704 |
| 13 | 338081920260 |
| 14 | 2670388231152 |
| 15 | 21109070463267 |
| 16 | 166980248599884 |
| 17 | 1321686452484286 |
| 18 | 10467203182893800 |
| 19 | 82936871755938970 |
[1,7,52,395,3036,23506,182904,1428387,11185900, 87789702,690212744,5434455182,42841215704, 338081920260,2670388231152,21109070463267, 166980248599884,1321686452484286, 10467203182893800,82936871755938970] |