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%I #6 Mar 30 2012 18:39:02
%S 0,-1,0,-2,1,0,-1,-3,3,-2,1,1,-2,3,-2,-6,5,-5,4,-2,3,-2,1,3,-3,4,-4,6,
%T -7,6,-7,-9,10,-9,10,-10,9,-8,9,-5,4,-5,4,-2,2,-1,0,8,-8,8,-7,9,-10,
%U 10,-9,13,-12,13,-14,12,-13,14,-14,-18,19,-20,19,-17,18,-19,18,-18,17,-16,16,-14,15
%N Det(M_n) where M_n is the n X n matrix m(i,j)=1 if floor(i/j) is even, 0 otherwise.
%C Det(Q_n) = 1 if Q_n denotes the n X n matrix defined by: m(i,j)=1 if floor(i/j) is odd, 0 otherwise, since this matrix is triangular with 1's on the main diagonal.
%o (PARI) for(n=1,70,print1(matdet(matrix(n,n,i,j,if((-1)^(sigma(i+j))+1,1,0))),","))
%K easy,sign
%O 1,4
%A _Benoit Cloitre_, May 30 2002
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