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A088829 Even numbers with even abundance. 5
6, 10, 12, 14, 20, 22, 24, 26, 28, 30, 34, 38, 40, 42, 44, 46, 48, 52, 54, 56, 58, 60, 62, 66, 68, 70, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 130, 132, 134, 136, 138, 140, 142, 146, 148, 150, 152 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Odd numbers with odd abundance are in A016754. Odd numbers with even abundance are in A088828. Even numbers with odd abundance are in A088827.

LINKS

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

EXAMPLE

Even perfect numbers are here.

n=10: sigma[10]=18, abundance=18-20=-2<0;

n=12: sigma[12]=28, abundance=28-24=+4>0.

sigma[n] is also even number; sign of abundance:<=>0.

MATHEMATICA

Do[s=DivisorSigma[1, n]-2*n; If[ !OddQ[s]&&!OddQ[n], Print[{n, s}]], {n, 1, 1000}]

CROSSREFS

Cf. A016754, A088827-A088828, A088830.

Sequence in context: A129493 A036350 A295076 * A036348 A100368 A128691

Adjacent sequences:  A088826 A088827 A088828 * A088830 A088831 A088832

KEYWORD

nonn

AUTHOR

Labos Elemer, Oct 28 2003

STATUS

approved

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Last modified April 3 04:21 EDT 2020. Contains 333195 sequences. (Running on oeis4.)