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%I #11 Sep 14 2013 12:34:16
%S 0,36,198576,427073321712,160091486928671945664
%N Number of city-block distance 1 permutations of a side-n hexagonal array.
%e Some solutions for n=3 (movement: 0=nw 1=ne 2=e 3=se 4=sw 5=w)
%e ...3.3.3.......2.5.3.......3.2.5.......3.2.3.......2.4.3
%e ..1.1.1.3.....4.5.4.0.....4.0.4.3.....4.0.0.5.....3.0.4.0
%e .1.3.2.4.4...3.1.1.2.5...1.3.1.3.0...1.4.2.4.4...1.5.2.0.4
%e ..0.0.0.4.....1.4.2.5.....3.0.4.0.....1.1.3.1.....3.2.5.1
%e ...0.5.5.......1.2.5.......0.2.0.......1.5.5.......0.2.5
%K nonn,hard,more
%O 1,2
%A _R. H. Hardin_ Sep 17 2012
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