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A204826
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Deficient numbers with odd sum of divisors.
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4
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1, 2, 4, 8, 9, 16, 25, 32, 49, 50, 64, 81, 98, 121, 128, 169, 225, 242, 256, 289, 338, 361, 441, 484, 512, 529, 578, 625, 676, 722, 729, 841, 961, 1024, 1058, 1089, 1156, 1225, 1250, 1369, 1444, 1521, 1681, 1682, 1849, 1922, 2025, 2048, 2116, 2209, 2312, 2401
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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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Deficient number 16 is in sequence because sigma(16) = 13 (odd number).
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MATHEMATICA
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aQ[n_] := OddQ[(s = DivisorSigma[1, n])] && s < 2n; Select[Range[2401], aQ] (* Amiram Eldar, Sep 02 2019 *)
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CROSSREFS
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Cf. A156903 (abundant numbers with odd sum of divisors), A204825 (abundant numbers with even sum of divisors), A204827 (deficient numbers with even sum of divisors).
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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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