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A091192 Abundant numbers having at least one abundant proper divisor. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
A080224(a(n))>1.
LINKS
Eric Weisstein's World of Mathematics, Abundant Number
EXAMPLE
24 is in the sequence since it is abundant, and 12 is a divisor of 24 which is also abundant.
MATHEMATICA
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 *)
PROG
(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
CROSSREFS
Sequence in context: A102505 A112064 A090440 * A067807 A224907 A292352
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Dec 27 2003
STATUS
approved

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Last modified March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)