

A292156


Triangle T(m,k) read by rows, where T(m,k) is the number of ways in which 1<=k<=m positions can be picked in an m X m square grid such that the picked positions have a line symmetry but no point symmetry.


9



0, 0, 0, 0, 0, 36, 0, 0, 168, 220, 0, 0, 524, 944, 1960, 0, 0, 1292, 2848, 6752, 15752, 0, 0, 2736, 7248, 20280, 55904, 120212, 0, 0, 5088, 15576, 48576, 156224, 378824, 1068008
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OFFSET

1,6


LINKS



FORMULA



EXAMPLE

The triangle begins:
0;
0, 0;
0, 0, 36;
0, 0, 168, 220;
0, 0, 524, 944, 1960;
0, 0, 1292, 2848, 6752, 15752;
0, 0, 2736, 7248, 20280, 55904, 120212;
.
The following configuration of 6 picked points from a 7X7 grid with a line (mirror) symmetry w.r.t. the line indicated by +++, but no point symmetry, is one of the T(7,6)=a(27)=55904 configurations with this property:
o o o o o o o
+ X o X o o o
X + o o o X o
o o + o o o o
X o o + o o o
o o o o + o o
o X o o o + o


CROSSREFS



KEYWORD



AUTHOR



STATUS

approved



