%I #14 Feb 16 2013 18:30:21
%S 6,5,7,3,4,2,1,9,8,9,8,1,5,6,7,4,3,2,3,2,4,8,9,1,6,5,7,5,7,6,2,3,4,9,
%T 8,1,8,1,9,7,5,6,3,2,4,2,4,3,1,8,9,5,7,6,7,6,5,4,2,3,8,1,9,1,9,8,6,7,
%U 5,2,4,3,4,3,2,9,1,8,7,6,5
%N A Sudoku torus.
%C The sequence is a listing for a Sudoku grid:
%C 6 5 7 3 4 2 1 9 8
%C 9 8 1 5 6 7 4 3 2
%C 3 2 4 8 9 1 6 5 7
%C 5 7 6 2 3 4 9 8 1
%C 8 1 9 7 5 6 3 2 4
%C 2 4 3 1 8 9 5 7 6
%C 7 6 5 4 2 3 8 1 9
%C 1 9 8 6 7 5 2 4 3
%C 4 3 2 9 1 8 7 6 5
%C No two diagonally adjacent elements are the same. If the grid is rolled into a cylinder either way, this is still true making a 'Sudoku torus'.
%C This extra information can be used to construct puzzles that use 'no diagonal' logic.
%C The two lexicographical Sudoki in the cross-references have one internal diagonal each and several external diagonals.
%H Mathworld, <a href="http://mathworld.wolfram.com/Sudoku.html">Sudoku</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Sudoku">Sudoku</a>
%e If a puzzle has say:
%e |x
%e 5|
%e ___|x
%e then x cannot be 5.
%Y Cf. A107739.
%Y Cf. A114288, A112454 (lexicographic grids).
%K nonn,fini,full,tabf
%O 1,1
%A _Jon Perry_, Jan 31 2013