login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Table of n, a(n) for n=1..36.

FORMULA

a(n) = A292153(n) - A291717(n) = A291718(n) - A292154(n).

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

Cf. A090642, A098485, A098487, A291716, A291717, A291718, A292152, A292153, A292154, A292155.

Sequence in context: A023929 A010113 A167264 * A265489 A262795 A309379

Adjacent sequences:  A292153 A292154 A292155 * A292157 A292158 A292159

KEYWORD

nonn,tabl,more

AUTHOR

Hugo Pfoertner, Sep 17 2017

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 16 21:55 EDT 2021. Contains 345080 sequences. (Running on oeis4.)