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A188486
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Numbers k such that abundance(k) is an odd square.
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4
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550564, 15038884, 57365476, 197686728, 257859364, 1027291978962, 4644774970276, 319916794343524, 694453849937352, 97695446432293264, 359108743507594276, 25158930569552222884, 39753480499724798884, 58696020670745146276, 1021872661864058163600, 1397225158602002109604
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OFFSET
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1,1
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COMMENTS
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Counterexamples to the Kravitz conjecture. Subsequence of A188484 with positive abundances. Abundances are A188488, sigma(k) - 2*k.
25158930569552222884 (found by Graeme Cohen) and 982150970230395945697746806666183824 (found by Sidney Kravitz) are also terms. - Amiram Eldar, May 17 2020
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REFERENCES
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Richard K. Guy, Unsolved Problems in Number Theory, 3rd Edition, Springer, 2004, Section B10, p. 74.
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LINKS
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CROSSREFS
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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