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 A229587 Number of defective 3-colorings of a 2 X n 0..2 array connected horizontally and antidiagonally with exactly one mistake, and colors introduced in row-major 0..2 order 1
 0, 6, 28, 116, 444, 1620, 5724, 19764, 67068, 224532, 743580, 2440692, 7951932, 25745364, 82904796, 265720500, 848179836, 2697594516, 8551948572, 27033340788, 85232507580, 268094978388, 841477302108, 2636009007156, 8242758323964 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Row 2 of A229586. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 Index entries for linear recurrences with constant coefficients, signature (6,-9). FORMULA a(n) = 6*a(n-1) - 9*a(n-2) for n>4. From Oboifeng Dira, Mar 04 2015: (Start) a(n) = 4*(3^(n-2) + 4*(2*n-3)*3^(n-4)) for n>2. G.f.: (x + x^3 + 2*x^4)/(1-3*x)^2 (except for first term). (End) EXAMPLE Some solutions for n=3 ..0..1..0....0..1..0....0..1..2....0..1..1....0..1..0....0..1..1....0..1..2 ..2..1..1....2..2..1....2..1..1....0..2..0....0..1..1....0..2..1....1..0..2 MATHEMATICA LinearRecurrence[{6, -9}, {0, 6, 28, 116}, 30] (* Harvey P. Dale, Mar 06 2023 *) CROSSREFS Sequence in context: A027106 A309717 A089096 * A230492 A026014 A332208 Adjacent sequences: A229584 A229585 A229586 * A229588 A229589 A229590 KEYWORD nonn AUTHOR R. H. Hardin, Sep 26 2013 STATUS approved

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Last modified November 30 11:40 EST 2023. Contains 367460 sequences. (Running on oeis4.)