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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 67 |
| 5 | 377 |
| 6 | 2235 |
| 7 | 13701 |
| 8 | 85947 |
| 9 | 548209 |
| 10 | 3540851 |
| 11 | 23093885 |
| 12 | 151793203 |
| 13 | 1004023273 |
| 14 | 6675725867 |
| 15 | 44581355765 |
| 16 | 298829626795 |
| 17 | 2009477057761 |
| 18 | 13550281076451 |
| 19 | 91594501130989 |
| 20 | 620471833255971 |
| 21 | 4211165312423001 |
[1,3,13,67,377,2235,13701,85947,548209,3540851, 23093885,151793203,1004023273,6675725867, 44581355765,298829626795,2009477057761, 13550281076451,91594501130989,620471833255971, 4211165312423001] |