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 A221667 Sum of neighbor maps: number of 2 X n binary arrays indicating the locations of corresponding elements equal to the sum mod 3 of their horizontal, diagonal and antidiagonal neighbors in a random 0..2 2 X n array. 1
 4, 12, 64, 256, 992, 4096, 16384, 65344, 262144, 1048576, 4193280, 16777216, 67108864, 268430336, 1073741824, 4294967296, 17179844608, 68719476736, 274877906944, 1099511513088, 4398046511104, 17592186044416, 70368743653376 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Row 2 of A221666. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 4*a(n-1) + 8*a(n-3) - 32*a(n-4) - 16*a(n-6) + 64*a(n-7). Empirical g.f.: 4*x*(1 - x + 4*x^2 - 8*x^3 + 16*x^6) / ((1 - 4*x)*(1 - 4*x^3)^2). - Colin Barker, Aug 10 2018 EXAMPLE Some solutions for n=3: ..0..0..0....0..1..0....0..1..1....0..1..1....1..1..0....0..0..1....1..0..1 ..1..1..1....0..1..0....0..1..1....0..1..0....1..1..1....0..1..1....0..1..0 CROSSREFS Cf. A221666. Sequence in context: A222645 A259816 A071769 * A275527 A222612 A339134 Adjacent sequences:  A221664 A221665 A221666 * A221668 A221669 A221670 KEYWORD nonn AUTHOR R. H. Hardin, Jan 21 2013 STATUS approved

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Last modified January 25 23:56 EST 2022. Contains 350572 sequences. (Running on oeis4.)