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%I #11 Sep 24 2013 12:07:20
%S 1,1,3,1,6,8,1,9,24,20,1,12,48,80,48,1,15,80,200,240,112,1,18,120,400,
%T 720,672,256,1,21,168,700,1680,2352,1792,576,1,24,224,1120,3360,6272,
%U 7168,4608,1280,1,27,288,1680,6048,14112,21504,20736,11520,2816,1,30
%N Triangle of absolute values of the coefficients (in descending powers) of the characteristic polynomials of n X n matrices with 3's on the main diagonal and 1's elsewhere.
%e 3rd row (1, 9, 24, 20) with alternating signs = characteristic polynomial 3 X 3 matrix [3 1 1 / 1 3 1 / 1 1 3], x^3 - 9x^2 + 24x - 20.
%Y Row sums are A006234: 1, 4, 15, 54, 189... Rightmost terms in each row = A001792: 1, 3, 8, 20, 48, 112, 256...(row sums of A103406, the analogous triangle with all 2's in the generating matrix.)
%Y See A103247 for another version.
%K nonn,tabl
%O 0,3
%A _Gary W. Adamson_, Feb 04 2005
%E Extended and edited by _John W. Layman_, Mar 17 2005