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A345702
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Numbers that can be written as 2*a^2 - 1 and 3*b^3 - 1.
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0
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-1, 647, 41471, 472391, 2654207, 10124999, 30233087, 76236551, 169869311, 344373767, 647999999, 1147971527, 1934917631, 3127772231, 4879139327, 7381124999, 10871635967, 15641144711, 22039921151, 30485730887, 41471999999, 55576446407, 73470177791, 95927256071, 123834728447
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OFFSET
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1,2
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LINKS
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FORMULA
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G.f.: x*(647*x^6+36942*x^5+195681*x^4+195716*x^3+36921*x^2+654*x-1)/(1-x)^7. - Alois P. Heinz, Jun 24 2021
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EXAMPLE
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647 = 2*18^2 - 1 = 3*6^3 - 1. Thus, 647 is in this sequence.
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MATHEMATICA
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Intersection[Table[2 n^2 - 1, {n, 300000}], Table[3 n^3 - 1, {n, 100000}]]
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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