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A243455
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Numbers n such that (n, sigma(n), tau(n)) lies on a sphere with integral radius centered at the origin, i.e., n^2 + sigma(n)^2 + tau(n)^2 is a square.
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0
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6, 61, 2089, 3606, 18585, 28710, 70981, 121374, 176529, 520320, 970783, 62788800, 114682878, 144653952, 174635334, 182054895, 3857228169, 4349012190, 15994971740, 17587660602, 22842677823, 65183331200, 66928439760
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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6^2 + tau(6)^2 + sigma(6)^2 = 36 + 16 + 144 = 196 = 14^2. So 6 is in the sequence.
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PROG
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(PARI) isok(n) = issquare(n^2 + numdiv(n)^2 + sigma(n)^2);
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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