Search: id:A002047 Results 1-1 of 1 results found. %I A002047 M1688 N0666 %S A002047 1,2,6,28,244,2544,35600,659632,15106128,425802176 %N A002047 Number of 3 X (2n+1) zero-sum arrays. %C A002047 This can be interpreted as the number of ways to choose 2n+1 cells in a hexagonal grid of side n+1 such that no two are in the same row or left diagonal or right diagonal. - Alex Fink (a00(AT)shaw.ca), Mar 16 2005 %D A002047 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %D A002047 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). %D A002047 B. T. Bennett and R. B. Potts, Arrays and brooks, J. Austral. Math. Soc., 7 (1967), 23-31. %D A002047 A. Kotzig and P. J. Laufer, When are permutations additive?, Amer. Math. Monthly, 85 (1978), 364-365. %H A002047 C. Bebeacua, T. Mansour, A. Postnikov and S. Severini, On the x-rays of permutations %e A002047 a(2) = 6 corresponds to %e A002047 ..O.X.X.......X.X.O.......O.X.X.......X.O.X.......X.O.X.......X.X.O %e A002047 .X.X.O.X.....X.O.X.X.....X.X.X.O.....X.X.X.O.....O.X.X.X.....O.X.X.X %e A002047 X.X.X.X.O...O.X.X.X.X...X.O.X.X.X...O.X.X.X.X...X.X.X.X.O...X.X.X.O.X %e A002047 .O.X.X.X.....X.X.X.O.....X.X.X.O.....X.O.X.X.....X.X.O.X.....O.X.X.X %e A002047 ..X.O.X.......X.O.X.......O.X.X.......X.X.O.......O.X.X.......X.X.O %Y A002047 Sequence in context: A006117 A118025 A119966 this_sequence A126340 A136639 A027109 %Y A002047 Adjacent sequences: A002044 A002045 A002046 this_sequence A002048 A002049 A002050 %K A002047 nonn,nice %O A002047 0,2 %A A002047 N. J. A. Sloane (njas(AT)research.att.com). %E A002047 More terms from Alex Fink (a00(AT)shaw.ca), Mar 16 2005 Search completed in 0.001 seconds