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A097579
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Triangular numbers k such that 2*k-1 is also a triangular number.
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0
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1, 28, 946, 32131, 1091503, 37078966, 1259593336, 42789094453, 1453569618061, 49378577919616, 1677418079648878, 56982836130142231, 1935739010345186971, 65758143515606214778, 2233841140520266115476, 75884840634173441711401
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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*(1-7*x+x^2)/((1-x)*(1-34*x+x^2)).
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MATHEMATICA
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CoefficientList[ Series[x*(1 - 7*x + x^2)/((1 - x)*(1 - 34*x + x^2)), {x, 0, 16}], x] (* Robert G. Wilson v, Sep 01 2004 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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