A146020 - OEIS

A146020

Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only in a 2 X 4 el 1,1 1,2 1,3 1,4 2,4 with any orientation.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 13, 13, 41, 41, 219, 219, 1033, 1033, 8217, 8217, 92671, 92671, 1241193, 1241193, 21102313

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,11

LINKS

Table of n, a(n) for n=1..27.

EXAMPLE

Maximal 11 X 11 example:

0 0 0 1 1 0 1 1 0 0 0

0 0 0 0 1 0 1 0 0 0 0

1 0 0 0 1 0 1 0 0 0 1

1 1 1 1 0 0 0 1 1 1 1

0 0 0 0 0 0 0 0 0 0 0

1 1 1 1 0 0 0 1 1 1 1

1 0 0 0 1 0 1 0 0 0 1

0 0 0 0 1 0 1 0 0 0 0

0 0 0 1 1 0 1 1 0 0 0

CROSSREFS

Sequence in context: A146426 A146051 A146229 * A145948 A049768 A209390

Adjacent sequences: A146017 A146018 A146019 * A146021 A146022 A146023

KEYWORD

nonn,more

AUTHOR

R. H. Hardin, Oct 26 2008

STATUS

approved