%I #11 May 12 2019 09:13:07
%S 1,0,3,0,2,9,0,1,12,15,0,0,12,39,25,0,0,4,59,96,35,0,0,1,42,210,188,
%T 49,0,0,0,21,255,550,332,63,0,0,0,4,212,954,1231,529,81,0,0,0,1,103,
%U 1184,2800,2406,800,99,0,0,0,0,33,964,4634,6818,4313,1142,121,0,0,0,0,6,546,5497,14182,14722,7171,1580
%N Triangle T(n,k) giving number of 3 X k polyominoes with n cells (n >= 3, 1<=k<=n-2).
%C Note that for k=3 (polyominoes with square bounding rectangle) these are not the free polyominoes, because Read does not apply the full symmetry group of order 8 to reduce the fixed polyominoes for c_q(n), but only the symmetry group of order 4 (excluding the 90 deg rotations). The free polyominoes with square bounding rectangles are the z_3(n) instead. - _R. J. Mathar_, May 12 2019
%H R. C. Read, <a href="http://cms.math.ca/cjm/v14/cjm1962v14.0001-0020.pdf">Contributions to the cell growth problem</a>, Canad. J. Math., 14 (1962), 1-20.
%e Triangle starts:
%e 1;
%e 0,3;
%e 0,2,9;
%e 0,1,12,15;
%e ...
%K nonn,easy,nice,tabl
%O 3,3
%A _N. J. A. Sloane_, Feb 05 2001
%E Values for n>=11 cells from _R. J. Mathar_, May 12 2019