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A204825 Abundant numbers with even sum of divisors. 4
12, 20, 24, 30, 40, 42, 48, 54, 56, 60, 66, 70, 78, 80, 84, 88, 90, 96, 102, 104, 108, 112, 114, 120, 126, 132, 138, 140, 150, 156, 160, 168, 174, 176, 180, 186, 192, 198, 204, 208, 210, 216, 220, 222, 224, 228, 234, 240, 246, 252, 258, 260, 264, 270, 272, 276, 280 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers m from A005101 such that sigma(m) = A000203(m) is even.

Complement of A156903 with respect to A005101 (abundant numbers).

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Abundant Number

EXAMPLE

Abundant number 12 is in sequence because sigma(12) = 28 (even number).

MATHEMATICA

aQ[n_] := EvenQ[(s = DivisorSigma[1, n])] && s > 2n; Select[Range[280], aQ] (* Amiram Eldar, Sep 02 2019 *)

CROSSREFS

Cf. A156903 (abundant numbers with odd sum of divisors), A204826 (deficient numbers with odd sum of divisors), A204827 (deficient numbers with even sum of divisors).

Sequence in context: A112769 A097320 A332956 * A111592 A111947 A109396

Adjacent sequences:  A204822 A204823 A204824 * A204826 A204827 A204828

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Jan 22 2012

STATUS

approved

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Last modified April 10 11:35 EDT 2021. Contains 342845 sequences. (Running on oeis4.)