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A210903 Number of n X n 0..2 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order 0
0, 1, 4, 78, 3740, 449340, 133337482, 98375439948, 180233106621896, 820210662659082911, 9270740885407976025652, 260267690197125447266436984, 18148375825241525659505646969576 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

Some solutions for n=4

..0..0..1..2....0..0..2..2....0..0..1..2....0..0..2..2....0..0..1..1

..0..0..1..2....0..1..1..2....0..0..1..2....0..1..1..1....0..0..1..0

..1..1..1..0....2..1..1..2....1..1..0..0....2..1..1..2....1..1..0..0

..2..2..0..0....2..2..2..2....2..2..0..0....2..1..2..2....1..0..0..0

CROSSREFS

Sequence in context: A296997 A220240 A246606 * A054951 A215843 A048957

Adjacent sequences:  A210900 A210901 A210902 * A210904 A210905 A210906

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 29 2012

STATUS

approved

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Last modified June 24 11:45 EDT 2021. Contains 345416 sequences. (Running on oeis4.)