A125493 Composite deficient numbers.

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

Offset: 1

Author

Tanya Khovanova, Dec 27 2006

Keywords

• nonn

Examples

			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.
		

Links

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

Crossrefs

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

Programs

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 *)

Extensions

More terms from Emeric Deutsch, Jan 01 2007