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A091192
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Abundant numbers having at least one abundant proper divisor.
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4
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24, 36, 40, 48, 54, 60, 72, 80, 84, 90, 96, 100, 108, 112, 120, 126, 132, 140, 144, 150, 156, 160, 162, 168, 176, 180, 192, 198, 200, 204, 208, 210, 216, 220, 224, 228, 234, 240, 252, 260, 264, 270, 276, 280, 288, 294, 300, 306, 312, 320, 324, 330, 336, 340
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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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24 is in the sequence since it is abundant, and 12 is a divisor of 24 which is also abundant.
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MATHEMATICA
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aQ[n_] := Module[{d = Divisors[n]}, Total@d > 2 n && AnyTrue[d[[2 ;; -2]], DivisorSigma[1, #] > 2# &]]; Select[Range[340], aQ] (* Amiram Eldar, Jun 21 2019 *)
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PROG
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(PARI) isabund(n) = sigma(n) > 2*n;
isok(n) = {if (isabund(n), fordiv(n, d, if ((d<n) && isabund(d), return(1)); ); ); return (0); } \\ Michel Marcus, Jun 21 2019
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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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