Abundance

Author

Eric W. Weisstein
April 1, 2011

This notebook downloaded from http://mathworld.wolfram.com/notebooks/NumberTheory/Abundance.nb.

For more information, see Eric's MathWorld entry http://mathworld.wolfram.com/Abundance.html.

©2011 Wolfram Research, Inc. except for portions noted otherwise

Code

Abundance[n_Integer?Positive]:=DivisorSigma[1,n]-2n
SetAttributes[Abundance,Listable]

Enumeration

Timing[Take[a=Abundance[Range[10^4]],100]]

Take[Position[a,_?Negative]//Flatten,100]

Position[a,-1]//Flatten

Position[a,0]//Flatten

Position[a,1]//Flatten

Take[Position[a,_?Positive]//Flatten,100]