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A125493 Composite deficient numbers. 3
4, 8, 9, 10, 14, 15, 16, 21, 22, 25, 26, 27, 32, 33, 34, 35, 38, 39, 44, 45, 46, 49, 50, 51, 52, 55, 57, 58, 62, 63, 64, 65, 68, 69, 74, 75, 76, 77, 81, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 105, 106, 110, 111, 115, 116, 117, 118, 119, 121, 122, 123, 124, 125, 128 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

22 is in the sequence because it is composite and its sum of divisors 1 + 2 + 11 + 22 = 36 is less than 2*22.

The integer 15 is in the sequence because it is composite and the sum of its proper divisors is 1 + 3 + 5 < 15. The integer 18 is not in the sequence because, although composite, the sum of its proper divisors is 1 + 2 + 3 + 6 + 9 > 18.

MAPLE

with(numtheory): a:=proc(n) if sigma(n)<2*n and bigomega(n)>1 then n else fi end: seq(a(n), n=1..160); # Emeric Deutsch, Jan 01 2007

MATHEMATICA

Select[Range[200], CompositeQ[#]&&DivisorSigma[1, #]<2#&] (* Harvey P. Dale, Mar 27 2016 *)

CROSSREFS

Cf. A002808 (composite numbers), A005100 (deficient numbers).

Sequence in context: A274584 A210998 A205524 * A164923 A141608 A243176

Adjacent sequences:  A125490 A125491 A125492 * A125494 A125495 A125496

KEYWORD

nonn

AUTHOR

Tanya Khovanova, Dec 27 2006

EXTENSIONS

More terms from Emeric Deutsch, Jan 01 2007

STATUS

approved

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Last modified October 19 04:40 EDT 2019. Contains 328211 sequences. (Running on oeis4.)