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A099944
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Number of 3 X n binary matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (00;1) and (11;0).
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0
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76, 164, 340, 692, 1396, 2804, 5620, 11252, 22516, 45044, 90100, 180212, 360436, 720884, 1441780, 2883572, 5767156, 11534324, 23068660, 46137332, 92274676, 184549364, 369098740, 738197492, 1476394996, 2952790004, 5905580020
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OFFSET
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3,1
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COMMENTS
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An occurrence of a ranpp (xy;z) in a matrix A=(a(i,j)) is a triple (a(i1,j1), a(i1,j2), a(i2,j1)) where i1<i2, j1<j2 and these elements are in the same relative order as those in the triple (x,y,z). In general, the number of m X n 0-1 matrices in question is given by (m+3)*2^(m+n-2)-2^n-2^(m+1)+4 for m>0 and n>2; for n=2 the number is (m+1)*2^m.
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LINKS
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FORMULA
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a(n) = 11*2^n - 12.
a(n) = 3*a(n-1) - 2*a(n-2) for n > 4.
G.f.: 4*x^3*(19 - 16*x)/((1 - x)*(1 - 2*x)). (End)
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MATHEMATICA
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LinearRecurrence[{3, -2}, {76, 164}, 30] (* Harvey P. Dale, Oct 22 2017 *)
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PROG
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(PARI) vector(50, n, i=n+2; 11*2^i - 12) \\ Michel Marcus, Dec 01 2014
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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