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Triangle T(n,k) = mobius(n/k)*phi(k) if k|n, otherwise T(n,k)=0; 1<=k<=n.
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%I #6 Mar 30 2012 17:25:15

%S 1,-1,1,-1,0,2,0,-1,0,2,-1,0,0,0,4,1,-1,-2,0,0,2,-1,0,0,0,0,0,6,0,0,0,

%T -2,0,0,0,4,0,0,-2,0,0,0,0,0,6,1,-1,0,0,-4,0,0,0,0,4,-1,0,0,0,0,0,0,0,

%U 0,0,10,0,1,0,-2,0,-2,0,0

%N Triangle T(n,k) = mobius(n/k)*phi(k) if k|n, otherwise T(n,k)=0; 1<=k<=n.

%F T(n,k) = sum_{j=k..n} A054525(n,j)*A130207(j,k), 1<=k<=n.

%e First few rows of the triangle are:

%e 1;

%e -1, 1;

%e -1, 0, 2;

%e 0, -1, 0, 2;

%e -1, 0, 0, 0, 4;

%e 1, -1, -2, 0, 0, 2;

%e ...

%Y Cf. A051731, A000010 (diagonal n=k), A007431 (row sums), A008683 (column k=1).

%K easy,tabl,sign

%O 1,6

%A _Gary W. Adamson_, Jan 17 2007