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 A220932 Equals two maps: number of n X 3 binary arrays indicating the locations of corresponding elements equal to exactly two of their horizontal and antidiagonal neighbors in a random 0..2 n X 3 array. 2
 2, 16, 92, 556, 3332, 19996, 119972, 719836, 4319012, 25914076, 155484452, 932906716, 5597440292, 33584641756, 201507850532, 1209047103196, 7254282619172, 43525695715036, 261154174290212, 1566925045741276 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 3 of A220935. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 5*a(n-1) + 6*a(n-2). Conjectures from Colin Barker, Mar 13 2018: (Start) G.f.: 2*x*(1 + 3*x) / ((1 + x)*(1 - 6*x)). a(n) = (2^n*3^(n+1) + 4) / 7 for n even. a(n) = (2^n*3^(n+1) - 4) / 7 for n odd (End) EXAMPLE Some solutions for n=3: ..0..1..0....0..1..1....0..1..0....0..0..0....0..0..0....0..1..0....0..0..0 ..0..0..1....1..0..1....0..1..0....1..0..1....0..0..1....0..0..0....0..1..0 ..1..1..0....1..0..0....0..1..0....1..0..0....0..1..0....1..1..0....1..0..0 CROSSREFS Cf. A220935. Sequence in context: A317451 A220324 A208002 * A207558 A207413 A271273 Adjacent sequences: A220929 A220930 A220931 * A220933 A220934 A220935 KEYWORD nonn AUTHOR R. H. Hardin, Dec 25 2012 STATUS approved

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Last modified September 8 05:26 EDT 2024. Contains 375751 sequences. (Running on oeis4.)