A000079 and the least deficient numbers

[Max]

Jack Brennen wrote:
>>  Is it trivial to show that there are no other least deficient numbers
>>  besides the powers of 2?  Do you have any references to the proof?
> 
> I haven't seen any proof of this.  It seems to be an open problem.
> See:  http://mathworld.wolfram.com/AlmostPerfectNumber.html
> 
> In particular, "The only *known* almost perfect numbers are the powers 
> of 2."

If so, the description of A000079 and MathWorld's "Least Deficient Number" article must be corrected.

Max