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A053229
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Numbers n for which second differences of sigma(n) are negative.
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5
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1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 104, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129
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OFFSET
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1,2
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LINKS
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MAPLE
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with(numtheory): seq(`if`(sigma(i+2)-sigma(i+1)<(sigma(i+1)-sigma(i)), i, print( )), i=1..133);
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MATHEMATICA
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Select[Range[150], DivisorSigma[1, # + 2] - DivisorSigma[1, # + 1] < (DivisorSigma[1, # + 1] - DivisorSigma[1, #]) &] (* G. C. Greubel, Sep 03 2018 *)
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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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