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A290583
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a(n) is the factor R(n) having prime factors < (2/3)*n^2 in A285388(n) = R(n)P(n).
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1
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1, 1, 15, 45, 28665, 119301, 5945469075, 349882586625, 37442407704398235, 16728192398775, 15367416005321626675, 25155676359358573576275, 8796919422969373203777212374275, 276042834397113472381083873409429425
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OFFSET
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1,3
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COMMENTS
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Prime factors > sqrt(2)*n occur with multiplicity 1.
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LINKS
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FORMULA
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EXAMPLE
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a(4)=45: A285388(4) = 300540195 = (R(4) = 3*3*5 = 45)*(P(4) = 6678671).
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PROG
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(PARI) a285388(n) = my(m=n*binomial(2*n^2, n^2)); m>>valuation(m, 2);
a(n) = my(f=factor(a285388(n))); for (k=1, #f~, if (f[k, 1] >= (2/3)*n^2, f[k, 1] = 1)); factorback(f); \\ Michel Marcus, Aug 07 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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