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 A210896 Number of n X n 0..2 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order 0
 1, 2, 20, 400, 16716, 1444348, 258951340, 96266852004, 74214689922928, 118642250445743920, 393305989512539553728, 2703723885515478100466476, 38542035415959856159523945096 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE Some solutions for n=3 ..0..1..0....0..1..1....0..1..0....0..1..0....0..1..0....0..1..0....0..1..0 ..1..2..0....1..0..2....1..0..2....1..2..1....1..0..1....1..0..2....1..2..0 ..0..0..1....1..2..0....0..2..1....0..1..0....0..1..0....0..2..0....0..0..2 CROSSREFS Sequence in context: A009236 A078698 A090728 * A090309 A002116 A058346 Adjacent sequences:  A210893 A210894 A210895 * A210897 A210898 A210899 KEYWORD nonn AUTHOR R. H. Hardin Mar 29 2012 STATUS approved

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Last modified January 22 16:29 EST 2020. Contains 331152 sequences. (Running on oeis4.)