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Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

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Claim. For every prime pp, every A⊆Fp∖{0}A\subseteq\mathbb F_p\setminus\{0\} with ∣A∣≤12|A|\le12 has an ordering whose partial sums are distinct, the question of Problem 475 for the sizes t≤12t\le12. This is Proposition 4.2 of S. Costa and M. A. Pellegrini, Some new results about a conjecture by Brian Alspach: the G-ADMS conjecture, their Conjecture 1.2, which asks exactly for an ordering of A⊆Zn∖{0}A\subseteq\mathbb Z_n\setminus\{0\} with distinct partial sums and which the paper attributes to Graham for prime nn, holds for subsets of size k≤12k\le12 of cyclic groups of prime order. The proof applies Alon's Combinatorial Nullstellensatz, in the manner of Hicks, Ollis and Schmitt, to a polynomial of degree k2k^2 encoding an ordering of a (k+1)(k+1)-set with distinct partial sums; for k=11k=11 two coefficients are computed, with greatest common divisor 232^3, so for every prime p>2p>2 one of them is nonzero modulo pp (p. 6 of the arXiv version), the case p=2p=2 being trivial. Corollaries 4.3 and 4.4 transfer the result to torsion-free abelian groups and to Zn\mathbb Z_n with all prime factors large. Read depth: claims checked for the statement in the arXiv version; the coefficient computation (Section 4.1 and the appendix) not replayed.

Covers. Every prime pp and every size t≤12t\le12. The sizes t≤11t\le11 were known before through Alspach's conjecture (the paper's references, Theorem 2.2 of Hicks, Ollis and Schmitt for k≤10k\le10 among them); the size 1212 is the paper's. Nothing about 13≤t≤p−413\le t\le p-4 for a fixed prime.

Depends on. Nothing in this wiki: the result is the paper's own, filed on its library result page.

Acceptance. Refereed publication: Archiv der Mathematik (Basel) 115 (2020), no. 5, 479--488, published online 29 August 2020 (Crossref record; the journal text is not held and was not compared with the arXiv version). The site's commentary credits the sizes t≤12t\le12 to this paper and its references, but the site's label DECIDABLE leaves the problem open and settles no part of it, so that credit is not reviewed evidence.