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Let . What is the smallest integer not representable as the sum of distinct unit fractions with denominators from ? Is it true that the set of integers representable as such has the shape for some ?
Let be sufficiently large and . Is the smallest integer not representable as the sum of distinct unit fractions with denominators from equal to or ? Is it true that the set of integers representable as such has the shape for some ?
Source: erdosproblems.com/308
An accepted solution exists. The statement is true.
Proved, in the site's label, which the site itself calls an essential solution; the standing on this page agrees, for the corrected Statement. The one claim page, Croot's Main Theorem (Mathematika 46 (1999), no. 2, 359--372; refereed; credited by the site), is an accepted full claim: it answers both questions of the corrected Statement. The theorem, in the author's typescript, gives for all large
Hence, for all large , is or (the second question is answered yes), and (the first question is answered yes), with the case decided by the fractional part of except when it lies between and times . The value inside that window, which Croot's conjecture (p. 2) would close, and the initial-segment property for every are the two variants the Formulation records. The site's discussion and proof-claim pages carry no further claim.
The site's wording, with "Let ", asks for the exact value
of the smallest non-representable integer for every , and whether
the representable integers form an initial segment for every . That is what
Erdős and Graham printed: [ErGr80], p. 39, for the set of integers of
the form with and
variable, asks "What is the smallest integer not in ? Is it true that
implies ?", with no range on . The site reads
the problem through Croot's theorem: its label is PROVED, its commentary says
the problem "was essentially solved by Croot [Cr99]" and concludes that, with
, the representable integers are "for all
sufficiently large, either or ";
the statement file it links as its formalization (formal-conjectures
308.lean, commit 9d259649abe0b02d7a25f7589b872db679b35e21) states the
problem as parts.i, for all large , and
parts.ii, the initial-segment property for all large , marks both solved,
and keeps the property for every as a separate open variant all_N;
the site's thread has no comments. The change replaces "Let " by "Let
be sufficiently large and ", in
the site's own notation, and replaces "What is the smallest integer not
representable ...?" by the question whether it equals or ; the
second question is unchanged. The answer under the site's reading is yes to
both, by Croot's Main Theorem (Mathematika 46 (1999), 359--372; typescript p.
1), which places between
and
for all large ,
so that and
; the site's two displays attach these floors to
where the theorem bounds , an off-by-one in the displays that does not
affect the site's consequence sentence. Under the readings the page does not
adopt: the exact value of is decided by the fractional part
of outside the window
(the upper threshold lowered to by the deduction from Yokota's
2002 Corollary 1 on its result page) and open inside it, where Croot's
conjecture (p. 2) that the upper floor is the truth would close it; and
whether is an initial segment for every is open, asserted by no
source, encoded by OEIS A101877 (the least largest denominator for each
integer, nondecreasing in its eight printed terms) and marked research open
by the formal-conjectures file. Both stay in Formulation with no claim page.
Results about the site's wording, credited and never counted: none; Boris
Alexeev's Erdos308.lean (plby/lean-proofs, commit
8822f7ddef30fadbd92e1c6ab4ed897af356af5e, 15 September 2026) states the
two-case statement for large , which is the corrected Statement, and is
unbuilt here. The page's standing judges the corrected Statement.