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A145450
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Numbers k such that k/A000005(k) is a square.
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1
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1, 2, 36, 108, 128, 225, 288, 441, 450, 600, 864, 882, 1089, 1176, 1521, 1944, 2000, 2178, 2601, 2904, 3042, 3240, 3249, 4056, 4761, 5202, 6144, 6498, 6561, 6936, 7569, 8649, 8664, 9522, 10000, 11760, 12321, 12696, 13122, 15129, 15138, 16641, 17298
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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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EXAMPLE
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36/A000005(36) = 36/9 = 4 = 2^2, hence 36 is in the sequence.
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MATHEMATICA
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Select[Range[20000], IntegerQ[Sqrt[#/DivisorSigma[0, #]]]&] Harvey P. Dale, May 21 2012
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PROG
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(PARI) {m=18000; for(n=1, m, s=sigma(n, 0); if(n%s==0&&issquare(n/s), print1(n, ", ")))}
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CROSSREFS
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KEYWORD
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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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