[seqfan] Re: Reference that "A027687 4-perfect numbers" is finite

[Robert Gerbicz]

"What is the reason to believe all 4-perfect are discovered (even if they
are finite)?"

>From the same link: "In March 2008 Achim Flammenkamp finally constructed
all MPNs < e350 by an exhaustive tree-search, i.e. proved that there are no
further but the 730 known MPNs"

And this bound is much larger than the largest known 4-perfect number. This
is the reason.

Note that this type of search is similar to the odd perfect number
searches, they use a similar tree-search method.