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 A285396 Start with a single cell at coordinates (0, 0, 0), then iteratively subdivide the grid into 3 X 3 X 3 cells and remove the cells whose sum of modulo 2 coordinates is 2; a(n) is the number of cells after n iterations. 6
 1, 21, 399, 7401, 136227, 2500437, 45845895, 840237393, 15396839067, 282119272221, 5169192919455, 94712719519353, 1735370171447763, 31796203000166949, 582583421696631159, 10674336158022192609, 195579614965832408523, 3583490696858688375405 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Cell configuration converges to a fractal with dimension 2.647... LINKS Peter Karpov, InvMem, Item 26 Peter Karpov, Illustration of initial terms (n = 1..4) FORMULA a(0) = 1, a(1) = 21, a(2) = 399, a(n) = 28*a(n-1) - 195*a(n-2) + 324*a(n-3). G.f.: (1-7*x+6*x^2)/(1-28*x+195*x^2-324*x^3). MATHEMATICA LinearRecurrence[{28, -195, 324}, {1, 21, 399}, 18] CROSSREFS Cf. A285395, A285394, A285393, A285392, A285391. Sequence in context: A145613 A212786 A015677 * A113363 A223459 A240655 Adjacent sequences:  A285393 A285394 A285395 * A285397 A285398 A285399 KEYWORD nonn AUTHOR Peter Karpov, Apr 19 2017 STATUS approved

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Last modified August 18 04:42 EDT 2017. Contains 290684 sequences.