A212130 - OEIS

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A212130

Number of n X n binary matrices with zero diagonal and no directed 3-loops (3-loop: x(i,j)*x(j,k)*x(k,i)=1, and i,j,k all different)

1, 4, 49, 1699, 156532, 36686047, 21135750421

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

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..7.

EXAMPLE

Some solutions for n=4

..0..1..0..1....0..0..1..0....0..1..0..1....0..0..1..0....0..0..1..1

..0..0..1..0....0..0..0..0....0..0..1..0....1..0..0..1....0..0..1..1

..0..0..0..1....1..1..0..0....0..0..0..1....0..0..0..0....0..0..0..0

..1..0..1..0....0..1..1..0....0..0..1..0....1..1..1..0....1..1..1..0

CROSSREFS

Sequence in context: A336805 A029991 A129419 * A049503 A159593 A263441

Adjacent sequences: A212127 A212128 A212129 * A212131 A212132 A212133

KEYWORD

nonn

AUTHOR

R. H. Hardin Jun 13 2012

STATUS

approved

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