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A245197
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Numbers n where tau(n) and n-tau(n) are perfect squares, with tau(n) the number of divisors of n (A000005).
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3
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1, 8, 85, 125, 365, 445, 533, 629, 965, 1685, 1800, 1853, 2340, 2605, 2813, 3029, 3973, 4765, 5045, 5220, 5629, 5933, 6245, 6893, 8285, 8653, 11029, 11453, 11885, 12773, 14165, 15133, 16645, 17165, 17460, 17693, 20453, 21029, 22205, 22805, 23413, 24653, 27229
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OFFSET
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1,2
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COMMENTS
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LINKS
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MAPLE
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filter:= proc(n) local t;
t:= numtheory:-tau(n);
issqr(t) and issqr(n-t)
end proc;
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MATHEMATICA
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okQ[n_] := With[{t = DivisorSigma[0, n]}, IntegerQ@Sqrt[t] && IntegerQ@Sqrt[n-t]];
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PROG
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(PARI) isok(n) = issquare(numdiv(n)) && issquare(n-numdiv(n)); \\ Michel Marcus, Jul 15 2014
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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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