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URL: https://oeis.org/A198471

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A198471
Abundant numbers that are smaller than the sum of their deficient divisors.
3
20, 30, 42, 66, 70, 78, 88, 102, 104, 114, 138, 150, 174, 186, 210, 220, 222, 246, 258, 260, 272, 282, 294, 304, 308, 318, 330, 340, 354, 364, 366, 368, 380, 390, 402, 426, 438, 450, 460, 462, 464, 474, 476, 498, 510, 532, 534, 546, 550, 570, 572, 580, 582, 606
OFFSET
1,1
COMMENTS
The primitive abundant number sequence (A071395) is a subsequence of this sequence.
LINKS
EXAMPLE
a(5) = 70 since 70 is smaller than 74, which is the sum of its deficient divisors.
MATHEMATICA
totdef[n_] := Total@Select[Divisors@n, DivisorSigma[-1, #] < 2 &]; Select[Range[570], DivisorSigma[-1, #] > 2 && # < totdef[#] &] (* Giovanni Resta, Jan 09 2013 *)
PROG
(PARI) isok(n) = (sigma(n) > 2*n) && (n < sumdiv(n, d, if (sigma(d) < 2*d, d))); \\ Michel Marcus, Jun 21 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Timothy L. Tiffin, Jan 07 2013
EXTENSIONS
a(21)-a(50) from Giovanni Resta, Jan 09 2013
STATUS
approved