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A213690 Half the number of (n+1)X(n+1) symmetric 0..1 arrays with no 2X2 subblock summing to 2 1
3, 13, 70, 529, 5148, 68798, 1220409, 29377751, 949700962, 41536397680, 2450653487731, 195553849371916, 21091722699002539, 3077853629320011499, 607688763160596614184, 162407853243770174812161 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A213697

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..18

EXAMPLE

Some solutions for n=4

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

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

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

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

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

CROSSREFS

Sequence in context: A024337 A001495 A284217 * A227117 A277922 A182189

Adjacent sequences:  A213687 A213688 A213689 * A213691 A213692 A213693

KEYWORD

nonn

AUTHOR

R. H. Hardin Jun 18 2012

STATUS

approved

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Last modified August 11 04:03 EDT 2020. Contains 336421 sequences. (Running on oeis4.)