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 A049475 Number of 2n X 2n matrices whose entries are {0,-1,+1} and whose row sums and column sums are all distinct. 5
 1, 4, 39, 2260, 1338614, 8522456190 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Matrices differing by taking transpose, multiplying by -1 and permuting rows and columns are regarded as equivalent. REFERENCES It is known (see references) that a (2n+1) X (2n+1) matrix of this form cannot exist. Rainer Bodendiek, Gustav Burosch; Streifzüge durch die Kombinatorik, Aufgaben und Lösungen aus dem Schatz der Mathematik-Olympiaden, (Excursions into Combinatorics) Spektrum Akademischer Verlag, Heidelberg, 1995, ISBN 3-86025-393-X Kapitel: Aufgaben zu Invarianten, Aufgabe 5.30, pp. 250-253. Fred Galvin, posting to sci.math, Date: 1999-09-25 - Solution to the antimagic 0,1,-1 matrix problem. LINKS Denis Cazor, Notes for a talk Denis Cazor, Programme Pascal Eric Weisstein's World of Mathematics, Integer Matrix EXAMPLE A 2 X 2 example: [ 1 1; 0 -1 ]. CROSSREFS Cf. A049526, A049527. Sequence in context: A203197 A094156 A266859 * A264084 A080271 A275361 Adjacent sequences:  A049472 A049473 A049474 * A049476 A049477 A049478 KEYWORD nonn,nice,hard AUTHOR EXTENSIONS Bodendiek-Burosch reference from torsten.sillke(AT)lhsystems.com a(6) from Denis Cazor, Dec 06 2017 STATUS approved

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Last modified September 23 22:32 EDT 2020. Contains 337315 sequences. (Running on oeis4.)