A127571 - OEIS

%I #6 Sep 17 2013 15:07:08

%S 1,1,3,2,0,4,2,3,0,7,4,0,0,0,6,2,6,4,0,0,12,6,0,0,0,0,0,8,4,6,0,7,0,0,

%T 0,15,6,0,8,0,0,0,0,0,13,4,12,0,0,6,0,0,0,0,18

%N Triangle T(n,k) = phi(n/k)*sigma(k) if k divides n, else 0.

%F T(n,k) = sum_{j=k..n} A054523(n,j)* A130208(j,k), product of the two infinite lower triangular matrices.

%F T(n,1) = A000010(n).

%F T(n,n) = A000203(n).

%e First few rows of the triangle are:

%e 1;

%e 1, 3;

%e 2, 0, 4;

%e 2, 3, 0, 7;

%e 4, 0, 0, 0, 6;

%e 2, 6, 4, 0, 0, 12;

%e ...

%Y Cf. A000203, A000010, A038040 (row sums), A054523.

%K nonn,tabl

%O 1,3

%A _Gary W. Adamson_, Jan 19 2007